The grey ghost a monster musume fanfic

by The agent of steel

Aiden Kurusu, known as the grey ghost of the navy seals has just been honorably discharged from military service and is now returning home to be with his brother Kimihito after nearly 8 years. however just like his brother, Aiden is going to get roped in by the inter species exchange bill and start to not only host extra species humans but also join the MON group as a new member.

1. Chapter 1 the Seal and the Oni

Chapter 1: the SEAL and the Oni

The sun hung low in the sky as Aiden, lieutenant in the United States Navy SEALs special response unit stood tall and proud in his navy seals dress uniform, his olive colored skin shining brightly in the sun and his short jet black hair glistening in the sun surrounded by his fellow comrades. The captain in charge stepped forward, his eyes filled with a mix of admiration and respect for the man before him.

"Today, we gather to bid farewell to one of the greatest soldiers this unit has ever seen," the captain announced, his voice resonating with pride. "Lieutenant Aiden, the Grey Ghost of Bermuda, and the Big Boss, your courage, dedication, and unwavering commitment to the mission have etched your name into the annals of history. Your missions in the treacherous jungles of Bolivia, the unforgiving deserts of Afghanistan, and the clandestine infiltration of Mongolia during operation Shrouded moon will be remembered for generations to come as events that would cement the unification and peace talks between demi humans and humans"

Aiden's stoic demeanor softened as he received the accolades, humbled by the praise from his commanding officer and comrades. The captain continued, "You've set a standard for excellence, leadership, and bravery that all recruits should strive to emulate. Your legacy will serve as a guiding light for the future of this unit."

Amidst the cheers and applause, the captain approached Aiden and shook his hand firmly. "Lieutenant Aiden, it has been an honor and privilege to serve with you. You leave behind a void that will be hard to fill, but we have no doubt that your next journey will be as remarkable as your time with us."

Aiden Saluted with his silver prosthetic arm, a reminder of what he had lost during his time of service and shouted, "it has been an honor Sir!"

With the formalities concluded, Aiden bid farewell to his fellow navy seals. As he made his way towards the base exit, a familiar figure emerged from the crowd. It was Jenkins, the sturdy minotaur who had fought by Aiden's side on countless missions.

"Hey, boss!" Jenkins called out, his deep voice carrying across the base. "What's the plan now? Gonna take a well-deserved break?"

Aiden grinned, turning to face his friend. "Well, Jenkins, I've heard my brother Kimihito is living alone in our parents' house in Japan. I think it's high time I pay him a visit and maybe spend some quality time together."

Jenkins chuckled heartily, clapping Aiden on the back. "Sounds like a great plan, boss. You deserve all the rest and happiness in the world."

"Thanks, Jenkins," Aiden replied sincerely. "And take good care of the squad. You're the best person to lead them now."

With a final nod to his squad mate, Aiden stepped into the waiting military Hummer that would take him to the airport. As he looked back at the base, he couldn't help but feel a mixture of nostalgia and excitement for the future that awaited him.

As soon as the hummer got to the airport the driver said, "once you make it to Japan you should be meeting with Agent Smith, good luck Big Boss its been an honor"

Aiden smiled and said, "you guys take care as well" before leaving to embark on his journey back to Japan.

As Aiden stepped off the plane In japan, he was immediately taken aback by the change in weather. The humidity hit him like a wall, making him feel like he had walked into a steam bath. Being used to the dry climate of Texas, this new environment was a stark contrast. He wiped his forehead and took a moment to adjust before continuing through the airport.

As he made his way towards the exit, he noticed the lack of demihumans around. Back in America, it was common to encounter them, but here in Japan, they seemed to be a rarity. The thought intrigued him, wondering how the culture and society here differed from what he was accustomed to.

Just as he was lost in thought, a familiar voice called out, "Aiden! Over here!" Turning, he saw Agent Smith standing with her MON squad. He smiled, glad to see a familiar face among the crowd.

"Aiden, it's good to have you here," Agent Smith said warmly, stepping forward to greet him.

"Thanks, Smith. It's been a while," Aiden replied, shaking her hand.

Smith then introduced him to the other members of the MON squad—Tionishia the ogre, Manako the monoeye, Doppel the doplleganger, and Zombina the living corpse, who had a skeptical look on her face as she eyed Aiden up and down.

"I'm not so sure about this guy," Zombina commented, crossing her arms. "He doesn't exactly look like a soldier are you sure this is the same Aiden you said stormed Mongolia."

Agent Smith chuckled lightly, coming to Aiden's defense. "Looks can be deceiving, Zombina. You should know better than anyone that appearances can be misleading."

Zombina raised an eyebrow, unconvinced. "I get that, but still..."

Agent Smith stepped closer to Aiden, placing a reassuring hand on his shoulder. "Let me tell you something about Aiden. The Navy Seals had a special group within their ranks who were one of the twenty-seven groups worldwide with clearance to deal with demihumans without violating the Interspecies Exchange Bill however they saw fit. Aiden here was hand selected for said group."

She looked around at her squad, emphasizing her point. "That means he's been through some serious stuff, and he's come out on top every time. I will admit though There's enough blood and black ink on his service records to drown the world a hundred times over. Don't underestimate him."

Aiden felt a mixture of pride and gratitude at Smith's words. He knew she had recommended him to the American navy, setting him on the path that led him to becoming a navy seal. Her support and encouragement had been instrumental in his career.

Zombina seemed to reconsider, looking at Aiden with newfound respect. "Alright, if you say so, Smith. I'll give him a chance."

"Good," Agent Smith replied, nodding. "Aiden has a lot to offer, and I believe he could be a valuable addition to the team."

Aiden smiled, grateful for the opportunity and eager to see what this new chapter in Japan would bring.

"you may be singing my praise Agent Smith but I have a feeling there is a reason you wanted to greet me personally at the gate" Aiden chuckled

"I'd like to offer you a position in my MON squad," Smith said, her gaze serious. "We deal with demihuman-related incidents, and your skills would be a valuable asset."

"I appreciate the offer, Smith," Aiden said, genuinely considering it. "But I also want to spend time with my brother. I haven't seen him in years."

Smith nodded understandingly, "Of course, family comes first. But keep the offer in mind". Before handing him a manila folder and saying, " I'm sure your skills would be beneficial not just in the navy seals, but also in the context of Japan's unique situation with demihumans."

"I will," Aiden assured her. "And thank you for everything you did for me back then. It meant a lot."

"It was well-deserved, Aiden. You've made us proud," Smith said, her tone sincere. "Now, go spend time with your brother. We can catch up later."

Aiden smiled warmly at Agent Smith, feeling grateful for the opportunities she had helped create for him before bowing and leaving on his way home

As Aiden approached his old child hood house, he couldn't help but notice how much bigger it seemed compared to his memories. He felt a mix of nostalgia and curiosity as he used his house keys to unlock the front door. As he stepped inside, he was taken aback to see a Lamia walking by in the living room. His Navy SEAL training kicked in instantly, and he switched into alert mode, assuming she was an intruder.

Reacting quickly, Aiden sprang into action, grappling the lamia to the ground, demanding to know what she was doing in his brother's house. "Who are you? What are you doing here?" he questioned, his voice stern and commanding.

Miia was startled and terrified, struggling to free herself from his firm hold. "Darling, help me! " she cried out, hoping someone would come to her rescue.

Hearing the commotion, Kimihito rushed out to the living room. Shocked to see his brother pinning down his Lamia guest, he quickly stepped in to defuse the situation. "Aiden! Hold on! It's not what you think!"

Aiden's eyes met his brother's, and he slowly eased his grip on the lamia, confused but recognizing the voice. "Kimihito? Is that really you brother?"

"Yes, it's me," Kimihito replied, relieved that his brother had returned home. "This is Miia. She's not a trespasser. She's here on a foreign exchange program."

Aiden's Navy SEAL instincts began to recede as he processed his brother's words. He got off Miia, taking a step back, still a bit flustered from the misunderstanding. "Foreign exchange program? For demihumans?"

Kimihito nodded, walking over to Miia to help her up. "Yes, exactly. Miia is living with me as part of a cultural exchange program. She's a friend, not a threat."

Aiden let out a breath he didn't realize he was holding, feeling somewhat embarrassed by his earlier reaction. "I'm sorry, Miia. I should've known better. It's just been a while since I've been home, and things have changed."

Miia, although shaken, managed to smile understandingly. "It's alright, Darling's brother. I understand. Just please be more careful next time."

Aiden nodded earnestly. "I will. I promise. And I apologize to you too, Kimihito. I didn't mean to cause any trouble."

Kimihito waved off his apology with a grin. "No worries, Aiden. It's good to see you again, bro. Welcome home. Dinners almost done come on in and relax, the other should be coming in soon."

Aiden nodded and followed Kimihito into the dining room and felt a mix of excitement and curiosity. He was about to meet the other girls living with his brother Kimihito, the girls he had heard so much about.

Kimihito stood up and motioned for Aiden to take a seat. "Everyone, this is my brother, Aiden. He's just back from the United States."

The first girl Kimihito introduced was Miia, the Lamia. She slithered over to Aiden and extended her hand, her eyes sparkling with curiosity. "Nice to meet you, Aiden. Kimihito talks about you a lot."

Aiden shook her hand with a smile. "It's great to meet you too, Miia."

Next was Papi, the Harpy, who fluttered over and perched on the back of a chair. "Hi there! I'm Papi. Nice to meet you!"

Aiden couldn't help but chuckle at Papi's adorable greeting. "Hi, Papi. You have some impressive wings there."

Suu, the Slime, extended a gooey hand and giggled. "Hello, Aiden. I'm Suu. Kimihito has told me a lot about you."

Aiden shook Suu's hand cautiously as it was a slime who took his left arm and said, "its good to meet you to kid"

Next came Centorea, the Centaur, who approached gracefully. "Greetings, Aiden. It's a pleasure to make your acquaintance."

Aiden stood up, slightly taken aback by Centorea's regal demeanor. "The pleasure is all mine, Centorea. It's impressive to see a centaur up close."

As Kimihito introduced each girl, Aiden learned more about them, their unique traits, and their quirky personalities. Rachnera, the Arachne, shyly waved from a distance, and Aiden gave her a friendly nod in return.

Finally, Kimihito turned to the last girl at the table, a stunning Mermaid named Meroune Lorelei. As she caught sight of Aiden, a glimmer of recognition shone in her eyes, and a smile tugged at her lips.

"It's been a while, my Grey Ghost," Meroune said in a melodic voice, surprising Aiden.

Aiden's eyebrows furrowed in confusion. "How do you...?"

Kimihito looked confused and said, "grey ghost?"

Meroune's smile widened, and she glanced at Aiden. "Oh its been ages if I remember correctly I was 17 at the time you saved me from those pirates off the coast of india"

Aiden's expression softened as the memory resurfaced. "Ah, yes. It was a dangerous mission, but I'm glad I was able to help."

The other girls looked at Aiden with newfound admiration, intrigued by the story behind the "Grey Ghost" nickname. They each took turns sharing a brief interaction with Aiden, expressing their gratitude or curiosity.

A Dullahan with pale white hair and dressed in armor then walked into the room and looked Aiden uneasy by him and said, "dear master this one reeks of death, who is he?"

Kimihito smiled and said, "oh lala this is my brother Aiden he was part of a covert navy seals team so your probably smelling the death from those days"

Aiden looked at lala and said, "so a dullhan lives here too, curious does that mean someone is about to die"

She pointed to Kimihito and said, "originally I assumed it would be him as he has this harem of crazed women however you…death has been going after you for years with no one to claim your soul, even the grimm reaper fears you, could it be you who is bound to die…Aiden the grey ghost?"

Aiden snickered and said, "death can try to claim me all it wants but I will not go quietly into the night if I am to die I will die on my terms and my terms only"

Rachnera blushed and said, "oh my what a bold man, I think I might be falling for him" before giving a glance at Kimihito as if to say, what are you gonna do about it.

Aiden chuckled, giving his brother a teasing glance. "Looks like you're slacking, Bro. All these beautiful girls, and you haven't made a move?"

Kimihito blushed, flustered by the comment. "W-Well, I... I'm just trying to take things one step at a time."

During dinner, the room was filled with laughter and joy as the group enjoyed each other's company. Aiden felt a strong bond forming with Kimihito's harem and was starting to appreciate the unique personality of each girl. Suddenly, Papi, the ever-cheerful Harpy, asked a question that caught everyone by surprise.

"So, how did you lose your arm, Aiden?" she chirped innocently while pointing at Aiden's left prosthetic arm, her curiosity getting the better of her.

The other girls looked at Papi with a shocked expression while Aiden started laughing.

Papi tilted her head, a little confused by the reaction. "Huh? Did I say something wrong?"

"No, not at all," Aiden assured her, his laughter subsiding. "It's just that it's not a common topic of conversation, especially during a meal. But, it's okay; I don't mind talking about it."

Curiosity piqued, the other girls leaned in, genuinely interested to hear his story.

"It happened during a mission," Aiden began, his tone turning more serious. "I was on a mission in a remote area, tracking down a dangerous variant of slime known as a black pudding. These slimes are highly corrosive, and their poison can be deadly. This one in particular had grown a sentient mind and had become…well it had become an assassin operating in France so US navy seals were sent in to take it down"

As Aiden narrated, the girls listened intently, their expressions reflecting a mix of concern and intrigue.

"I got too close it, and it managed to bite me," Aiden continued. "I knew I had to act fast. The poison was spreading rapidly through my arm, and I had to make a quick decision."

He paused for a moment, his gaze drifting to where his left arm should have been. "I took out my combat knife and made a split-second choice to cut off my arm above the bite mark. It was a tough call, but it saved my life."

Aiden noticed Suu's reaction and immediately realized how his answer might affect her. He reached out and gently placed a hand on her slimy shoulder. "Hey, it's okay, Suu. Don't be upset. It's not your fault."

Suu looked up at him with her big, expressive eyes, her voice trembling slightly. "But... it was a slime that hurt you. I'm a slime too, so you must hate me, right?"

Aiden's heart sank at Suu's words. He didn't want her to blame herself for something that wasn't her fault. "Suu, listen to me," he said softly. "You are not to blame for what happened. The black pudding slime that bit me was a dangerous variant, and its actions were not a reflection of all slimes."

He smiled reassuringly at her. " I don't hold any grudges against you or your kind."

Suu's eyes glistened with tears of relief and gratitude. "Really?"

"Really," Aiden confirmed, giving her shoulder a gentle squeeze.

The other girls looked on, touched by Aiden's words and his genuine care for Suu. Miia smiled at her fellow housemate, proud of him for comforting Suu in such a compassionate way.

As the tension dissipated, the dinner continued with a renewed sense of camaraderie. Aiden chatted with the girls, learning more about their personalities and interests. Papi's initial question, though surprising, had allowed them all to deepen their understanding of one another.

Throughout the night, Suu stuck close to Aiden, grateful for his acceptance and kindness. Once Dinner was done and the girls left to go and get ready for Bed Aiden stayed in the living room with his brother to chat.

Kimihito chuckled and said, "so bro I assume you're done with military service?" before getting up to make them both some coffee

Aiden nodded and said, "yeah I was honorably discharged yesterday".

Chuckling Kimihito said, "so I guess that means you're moving back in which explains why agent smith renovated the entire house again"

Aiden raised his eye and said, "again?"

Kimihito nodded and said, "when Miia arrived they made the house a lot larger to accommodate her size, and then they did it again to accommodate Mero and then they came by this morning and renovated it again for an additional 10 rooms however according to smith that was an error on her part as it was only supposed to be one extra room."

Aiden laughed and said, "that explains why the house looks so big but yeah I am moving back in but I do have a job lined up so I can start paying rent."

Kimihito waved his hand and said, "no, no, no you are my brother there is no need for you to be paying rent"

Aiden looked at Kimihito and said, "brother, mom and dad left you the house making you the sole owner however I am your older brother so respect my wishes and let me pay you $350 monthly for rent"

Kimihito smiled and said, "guess I can't talk you out of it, anyways what is the job anyways?"

Aiden then pulled out the paper work smith had handed him at the airport and said, "Agent Smith has hired me to be a special operative working for the MON neutralization squad, as an ex-navy seal I still have my name etched in the records as someone with clearance to harm demi humans so I would be perfect for the job"

Kimihito smirked and said, "well I wish you the best of luck brother I'll be turning in for the night you should to"

Aiden looked outside to see it was the dead of night and said, "you have a point brother I will see you in the morning" before heading off to his new room at the very top of the house which he had claimed as him.

It may have been a barren room, but it was like a second master bed room with a beautiful balcony over looking the street. At one point this area was filled with smaller houses, but as relations with demihumans started to flourish the houses and yards had to get bigger to accommodate them all causing this one small neighborhood to adopt the old American idea of having private land and a house.

Aiden chuckled and said, "it is good to be home" before going into his suitcase and pulling out a laptop and a sleeping bag to order some furniture off of Wamazon for his new room.

The next morning Aiden woke up grogy and in pain, sleeping on the cold hard floor in a sleeping bag is not something he liked even though he did it hundreds of times while serving as a navy seal. Stumbling into the kitchen, still rubbing the sleep from his eyes, he had one thing on his mind – coffee. He needed that caffeine boost to wake him up properly. As he reached for the coffee pot, he froze in surprise.

There, sitting inside the coffee pot, was Suu. Her translucent blue form blended perfectly with the water, making her almost invisible. Aiden couldn't help but let out a startled yelp, which only made Suu giggle mischievously.

"Good morning, Aiden!" Suu said cheerfully, her voice emanating from the water-filled coffee pot.

Aiden blinked a few times, trying to process what he was seeing. "Suu, what are you doing in there?"

"I was just enjoying a nice drink of water," Suu replied, suddenly shooting out of the coffee pot and landing right in front of Aiden taking on her human voluptuous form.

Aiden chuckled, shaking his head. "You scared me for a moment there. I thought the coffee pot had come alive or something."

Suu grinned,. "Sorry about that, Aiden. I couldn't resist having a little fun."

Aiden couldn't help but smile at Suu's playful nature. She was unlike anyone he had ever met, and her ability to morph and hide in plain sight never ceased to amaze him.

"Well, just be careful not to scare me too much next time," Aiden teased, pouring some water into the coffee pot to refill it. "I need my coffee to wake up properly in the mornings. And I don't want to accidentally switch into combat mode like I did with Miia"

Suu pouted playfully. "But water is so much better!"

Aiden chuckled, understanding her enthusiasm for water. "That may be true, but coffee is my thing. My elixir of life"

As he brewed a pot of Hawaiian hazelnut coffee, the rest of the household started to wake up, and soon the kitchen was filled with the chatter of the other girls.

First Rachnera walked in and said, "aahhh Aiden your up awfully early have any big plans for the day?"

Aiden pulled out his phone and realized a bunch of packages were on the way for him and said, "yeah got some stuff coming in today for my room, other than that I got nothing."

Rachnera giggled and said, "well I hope you have fun~ maybe I'll come by and give you a hand with things" before blowing aiden a kiss and sitting down to watch some news.

Aiden sat down at the table with his cup of coffee, feeling more awake now thanks to the caffeine.

Suu joined him at the table, "Can I try some of your coffee, Aiden?"

Aiden smiled and offered her a sip, making sure it was cooled down enough for her. Suu eagerly slurped it up, her face lighting up with delight.

"Mmm, this is interesting!" Suu exclaimed, enjoying the new flavor.

That's when the caffeine hit her and hit her like a damn school bus.

Suu started to rush around happily laughing and full of energy like a child before grabbing Papi and shouting, "let's go have some fun in the yard!"

This made Aiden Laugh as he watched the two energetic kids rush out.

"ahh someone seems to be in a good mood" Kimihito chuckled walking in.

"I have to hand it to you brother you have some interesting people living here but they seem like good people, and I respect that."

Kimihito looked at Rachnera who was tying up Lala in BDSM knots and said, "they can be a handful, but I would be lost without them"

Soon though the doorbell rang. Kimihito excused himself to answer the door.

To his surprise, Agent Smith from MON stood at the door, accompanied by a large Oni with mesmerizing violet eyes, voluminous, deep crimson hair, and a curvaceous well-endowed figure, "Hello, Kimihito. I hope I'm not interrupting anything important," Agent Smith said with a professional smile.

Kimihito shook his head, "No, not at all. Please, come in."

Agent Smith entered the living room, and the Oni followed closely behind. "I have some news," Agent Smith continued, "Kiyomi here needs a host family, and I've assigned her to stay with Aiden."

Aiden's eyes widened in astonishment, not expecting to be assigned as a host family for a demihuman. He looked at Kiyomi, who seemed both shy and excited at the prospect. "Me?" Aiden asked, pointing to himself. "But I'm just visiting my brother here."

Agent Smith smiled knowingly, "You're still part of the family, Aiden. And with your experience in dealing with demihumans during your service, I believe you'll make an excellent host for Kiyomi."

Kiyomi approached Aiden with a blush on her cheeks. "Thank you so much, Aiden-san," she said, hugging him warmly, it may have seemed like a warm hug but in all honesty, she was practically smothering Aiden between her fat tits.

Stuttering a bit Aiden said, "I am honored to be called your master, but would you kindly let go of me before you smother me to death!"

Kiyomi blushed and stuttered saying, "o-oh right sorry about that!" before letting go of him allowing aiden to breathe.

Kiyomi took a deep breath, attempting to change the topic. "So, what's there to do around here? I'm up for anything!"

At that moment Lala had walked in and noticed Kiyomi's luggage and said, "do I see a video game power chord sticking out of your suitcase?"

Kiyomi nodded and opened her luggage to reveal she didn't even have any clothes or anything packed, all she had was video game consoles and games galore. "hehe they- they told me to pack important things so I chose my video game collection"

Soon Kiyomi had found herself an empty room to set up a sleeping bag and her consoles onto a small portable tv and Aiden decided to go out with Kimihito to go and get some furniture for her room but also ended up getting a huge bed with the sofest mattress ever along with some tvs, monitors and even a whole desktop set up just for aiden's room as he still wanted to be connected to his buddies in the field.

Rushing back home with all these good Aiden and Kimihito made sure that Kiyomi was distracted so they could set up her room. Aiden took the initiative using the file Smith had given him all about Kiyomi's personality and such and made a room fit for an Oni Gamer with a big PC set up a plasma screen tv plenty of bean bag chairs and stuff and even a minifridge for those late-night gaming sessions.

Kimihito looked at Aiden and said, "how are we paying for all this?"

Aiden pulled out an American Express platinum card (not sponsored) and said, "been a member for 6 years now bro I'll pay for everything"

Kimihito got on his knees and bowed down to Aiden and said, "thank god!"

This made Aiden chuckle but the two of them soon went down to a sight that gave the men a nose bleed. Suu had spread out Kiyomi using her slime body as restraints and was currently trying to suck out the moisture from her now exposed breasts.

Moaning in pleasure Kiyomi was saying, "n-no please ahhh Suu not there I am sensitive there!" while suu looked to be trying to into Kiyomi's womanhood.

Aiden looked at Kimihito and said, "bro does- does this happen daily!"

Totally unphased and now rushing to help Kiyomi out of Suu Kimihito nodded and said, "yep daily!"

Aiden snapped out of it and helped remove Kiyomi by spraying suu's appenedges with a strange gas which froze suu.

Suu looked like she was about to cry when she finally let go of Kiyomi and said, "w-what was that?"

Aiden sighed and said, "my apologies suu I didn't mean to hurt you, that was nitrous gas, it freezes on contact and had been my tool in the navy to deal with slimes"

Kiyomi finally composed herself enough to get up with shaky legs and said, "s-so wanna play some games Master?" smiling at Aiden.

Aiden nodded and said, "I'll show you what me and my brother did to your room"

As soon as they got into her room her eyes started to sparkle in awe of the room and the stuff Aiden had put inside it to make her feel more at home. Soon Aiden and Kiyomi were sitting down in some bean bag chairs talking about games and such unaware they were being watched. As they chatted about games and hobbies, Suu couldn't help but feel a little left out. She looked at Kiyomi with sad, gooey eyes, feeling a bit down that she couldn't join in the conversation.

Kiyomi noticed Suu's expression and immediately tried to include her. "Hey, Suu, do you like playing games too?"

Suu tried to form a thumbs-up with her gooey hand. "I do, but... I'm not great with electronics."

Kiyomi grinned, not one to let anyone feel left out. "No worries, Suu! We can find something fun for you to join in too!"

Aiden shouted, "I swear to god if you bring out dance dance revolution, I am going to throw a shoe at you!"