Note: This is just a story idea, just want to see how it works out.

Anyway, Happy Lunar New Year

Summary: It happened again. He lost and as a result the people he cared about got hurt in the process… So when given the chance to save the girl he loved, he took it without hesitation and decided to use all the resources he had to make it possible… even if it meant that he could no longer run away from his past and his responsibilities… as Vongola Decimo.

Highschool Mafia: Devil X Decimo

Chapter 1

Tsunayoshi Sawada

The first thing that Issei saw when he woke up, was a family roof above him.

"So I'm back here huh…" The Pawn of Rias Gremory let out a sigh as he recalled what happened. He had been participating in a battle, the [Rating Game] between his master Rias Gremory and her unwanted fiancés Raiser Phenex, to decide whether or not she would have to marry him on the marriage engagement that the two families had set up for them. The stage had been the replica of the school that he attended.

Their base had been the old school building, and he had been running across the battlefield along with Kiba Yuuto and Koneko Tojou, the Knight and Rook of Rias, aiming for the enemy's base which had been the new school building.

But one by one, Koneko had fallen, Kiba had fallen and Akeno-san had fallen… and then…

As he tried to push his body up, his intuition, something that he had been suppressing constantly whenever he was awake for the past three years, resurfaced and told him that there was someone else in his room. When he turned his head, the brunette saw a woman standing in the shadow, but he knew who she was.

"Grayfia-san…" He acknowledged her.

"It looks like you're awake." The silver haired maid nodded her head as she walked closer to him.

"The game? What happened to Buchou?" He asked, his tone surprisingly calm which made Grayfia look at him with a hint of surprise in her silver eyes for a second before she answered.

"Raiser-sama won the match. Rias-Ojou sama resigned. "

Issei could only curse in his mind, as the pawn found himself completely speechless. So he had lost? He had been beaten by Raiser.

For the first time in three years… Issei felt useless.

He had acted so great, and yet he couldn't do anything and went down in front of his master...

'Why am I weak so weak… even after all this time?' the brunette thought bitterly as he grabbed his head. Even Asia could have continued to live as a human if he had been a little stronger at that time, if he hadn't hesitated.

Even for Rias, if only he could have used his Sacred Gear more effectively, or he had had enough courage to use the power that he had locked away for her… then everything he wouldn't have ended like this...

Memories flashed in his mind, as Issei remembered the people that had fallen that day for him just because he had been weak, unable to stop himself from crying. Even though Grayfia was standing at his side, he didn't try to stop the tears from flowing freely. But at the same time, he was frustrated, at himself and his lack of capability to make decisive decision… even after all this time.

"Currently, the engagement party for Ojou-sama and Raiser-sama is going on." Grayfia said "It is in the Underworld ballroom that was prepared by the House of Gremory. "

"Where are Kiba and the others?" He asked, wiping the tears away with the back of his hand.

"They went to escort Ojou-sama. The only ones who are not in the hall that are related to them are Issei-sama and Asia-sama." The silver haired woman answered "Due to Rias-sama's desire, Asia-sama stayed here with me looking after you, Issei-sama. She came down to get you a new towel." She then paused for a second before asking, a question that she seemed to keep until now "Can't you agree with that? Rias Ojou-sama's wedding."

"Yes. Even if the battle is over, I can't accept that."

"Do you know that Rias-ojou sama obeyed the family's decision?"

"I understood that! I know that! Even so I ..." It's true, he could never agree with something that his master was against.

"Fufufu". Suddenly, Grayfia laughed softly, making the brunette turn his head to look at her in surprise. It was his first time he had seen her smile.

"You are a very interesting person, Issei Hyoudou-sama. This is my first time that I have seen someone like you who shows what you are thinking with your face, and acts according to what you believe. My master, Sirzechs-sama, was watching your effort in the battle from elsewhere and said that you were interesting, you know?" Grayfia then reached her hand into her skirt pocket and took out a single paper, which had a magic circle written on it. "This magic circle allows you to teleport to the engagement party hall of the House of Gremory and the House of Phoenix."

"I have a message from Sirzechs-sama for you." She pauses for a second and then speaks with a straight face. "If you want to save my sister, go into the hall. That was what he said. There is also another magic circle on the back of the paper. Please use this when you take Ojou-sama back. I'm sure it will be useful for you. "

Issei was speechless. He didn't know how to respond. Grayfia then left the paper with the magic circle in his hand before she got up and took her leave from his room.

"When you were sleeping, I could feel an enormous power within you, Issei-sama. I know there's a dragon inside of you, but this power is something else entirely… I have felt it before, so I know well that if you are someone who can use that kind of power to its fullest potential then… I believe that you can do it." And with that, Grayfia turned around and left my room, leaving Issei behind to ponder what she had just said to him.

However, there was no need to decide whether or not he should go to the Underworld and save his master.

Without a second thought, he made his decision. He would not run away anymore. If it meant that he could save his master, then he would gladly sacrifice everything that he had tried to do the past three years.

Issei got up from his bed and went to look for his phone and something to wear.

But before he could make the call, the door opened and Asia entered.

"—! Ise-san! " As soon as Asia sees hi, the former nun left the towel and bucket of water on the floor to jump into his arms.

"Wow. Hey Asia, what's wrong?" He couldn't help but ask, feeling a bit ashamed when Asia suddenly hugged him like this

"Thank God. I'm so happy. You slept for two days, even when your wounds were healed ... I thought you would never open your eyes again ... Ise-san ..." The blond began to cry in his arms, and Issei couldn't do anything but try to calm her down while stroking her head.

"Asia, listen to me. I am going to Buchou's side now."

"!" Asia looked up in shock as what he just said, immediately realizing what he was about to do.

"Yes, I will take you back to Buchou. It's not a problem. I have my hands on a ticket to go to the hall."

"I'm going too!" Asia said seriously without thinking twice.

"You cannot. Please stay here Asia."

"I don't want to! I can fight together with you, Ise-san! I learned to use my demonic powers! I don't want to be just protected anymore!" Asia said as she grabbed onto his hand.

The pawn just shook his head: "No. You're staying, Asia. I'm going to bring Buchou back. It's okay. I'm going to hit Raiser easily and..."

"It is not alright!" Asia raised her voice, almost scream. There were tears coming out of her green irises, and she had a very sad face. "You'll be bleeding, bruised and limp again. Why do you have to go through all that pain again...? I don't want to see Ise-san in that state again…"

While putting on a big smile, Issei grabbed Asia's hand. "I will not die, Asia. Absolutely. I promise. Remember how I was alive when I saved you? That's why I'll be fine. I will not die. I will live and I will be with you from now on."

Asia stared up at him for a long second before nodding, wiping away her tears before continuing "If so, please promise me one more thing."

"Promise?"

"Please, definitely come back with Buchou-san."

"Yes of course." When he answered it like that, Asia smiled very happily. "now, if you excuse me… I need to make an important phone call." He said and then opened his phone to dial a number before placing it at his ear to wait. the former nun just looked at him curiously.

He did not have to wait long.

"Yes, Gokudera-kun, calm down. It's me." He said with a small smile, eyes closing "Listen, I will explain everything later. Right now, I need your help. How fast do you think you can gather everyone and get to Kuoh? I know that we have lost everything but... Just try to bring the guardians together. Also, do you know how well the mafia world is involved with the Devils?"

Break

"Yuuto-kun, where is Issei-kun?" Akeno Himejima asked while looking around, dressed in an elegant dark colored kimono with pink floral patterns and yellow obi, the Queen of Rias Gremory was drawing quite a lot of attention from the male population around her. "I thought he was coming with you."

"He hasn't woken up yet, Akeno-san." Kiba answered, leaving Akeno to nod her head sadly. He was dressed in a black tuxedo that fit him well. Like Akeno, he was also receiving a lot of attention from others, but mostly from the female devils all around him.

"Time." Koneko's short informant made all three members of Rias' Peerage turned their head to look at the main stage of the ballroom, where a yellow magic circle appeared over the one of Gremory Household before busting into flame. Raiser Phenex the emerged with a smug grin on his face, wearing a fine outfit that exposed his torso.

"This is truly a wonderful day." He announced loudly and confidently "It's not just the day of my wonderful wedding but also the unity of two powerful families. Everyone, let me present you my queen, Rias Gremory." The blond declared and out stretched his arm to the side, where the red magic circle on the floor flared.

Rias Gremory appeared out of the circle in her white wedding dress, looking extremely stunning and beautiful that immediately captured the hearts of everyone in the room.

But her eyes were closed, and her head was lowered in defeat.

Just then, the door of the Hall was kicked open, causing all the high class devils in the ballroom to turn their heads and look at it in surprise, no one more so than the crimson haired heiress herself. If one looked closely enough, they could see a feeling of hope in her eyes as well.

However, the one who stood on the other side of that that door was not someone she or anyone had expected, but a tall young man with silver hair that dressed himself formally in a black suit and a matching colored tie over a red shirt, being accompanied by different types of accessories such as wristbands and rings.

All the devils immediately became alerted to his presence, because he was holding one of the guards by the collar of his shirt while standing over another that seemed to have passed out after being beaten. The silver haired teen then dropped the guard and walked into the room, where he was instantly being accompanied by a group of men wearing dark suit and glasses.

"Which one of you is Rias Gremory-sama?" He asked, loud enough for everyone in the room to hear as the men behind him came to stand in two straight lines, hands behind their backs.

"I… I am." Rias spoke up, but she did not make any attempt to walk toward him. "What business do you have with me?" She couldn't help but ask, but the teen merely smirked in response before he turned back to the door. It was at that moment everyone heard the sounds of footsteps outside, drawing closer and closer.

When he appeared in the hallway before them, almost instantly the silver haired teen and the suited men bent over to bow their head low to that person, shocking everyone who knew or recognized him. "Boss!" the said at the same time.

The person then walked further into the room, adjusting the cuff of his long sleeve shirt, worn underneath a black, formal suit similar to the one the others were wearing. He then came to stand beside the silver haired young man, and smiled at him, placing a hand on his shoulders as he said with a small, gentle smile:

"Thank you, Gokudera-kun. But this is not needed."

"Yes, Juudaime! I promise this won't happen next time."

"Ise?" Rias finally blurted out, looking at her Pawn who looked up and smiled at her.

"Guards!" Raiser suddenly spoke up while pointing his hand at Issei "Remove them from this instance!" Instantly, a number of guards rushed toward them, but Issei remained still on his feet, holding one arm out to stop Gokudera, who growled in annoyance and was about to charge at the guards with the rest of the black suited men.

Before any of them could reach the brown haired teen or Rias' peerage could rush in to help their friend, two other men ran into the room in blurs, and stopped the guards on their ways, defeating them swiftly with their fists and weapons. The first, was a teenager with tanned skin, gray eyes, and white hair, with a scar on his left temple, an adhesive bandage on his nose, and the sports tape around his arms like that of the boxers. The second was a fairly-tall young man with short, spiky black hair and large brown eyes, wielding in his hand a long katana, which he used to swiftly parry the weapons of the devil guards, and defeated them with flawless lightning fast strikes. Like Gokudera, they were dressed in black suits.

"You two are late!" the silver haired teen growled in annoyance while crackling his knuckles at them.

"Now now, we ran into a little bit of trouble with the guards outside. They are tougher than they look." The sword wielder laughed casually as he twirled his sword around and put it on his back.

"Anyone else?" The short hair teen asked as he punched away a guard on his side with a strong left hook, which was so powerful he knocked him away and the ones behind him, effectively taking them all down. Once he had seen that al the guards had been defeated, he stood up and punched his fist, smirking widely at the brown haired teen standing next to him "Hey Sawada, it's your turn."

"I know, thank you Yamamoto-kun, onii-san." Issei nodded before he stepped further into the room, announcing loudly with each step "Some of you here might know me as Issei Hyoudou… but my real name is Tsunayoshi Sawada. I'm the Tenth Boss of the Vongola Famiglia."

"And I have come here today to take back Rias Gremory."

End of Chapter 1

Note: If you don't like the basic idea of this story and how it start out, then no need for you to be here. Don't need to tell me how much you don't like it either. This is just an idea that I want to work with in this very not active crossover fandom.

If you can accept the plot holes as unncessary and ignore them for the sake of the story following with the next chapters, welcome and I hope you will have a great time reading