In Mikado City, home to 280,000 people, a Gate to another world opened one fateful day.

Invaders from another dimension known as "Neighbors" poured through.

The city then knew true fear.

The Neighbors' technology makes them immune to most Earth weapons. Most believed the fall of the city was only a matter of time.

But then...

A mysterious group drove off the invaders and delivered a message.

"Leave the Neighbors to us. We have long trained for this."

They studied Neighbor technology and created an organization to defend the world from them.

The defense organization that was known as Border.

The group built a tremendous base in a very short time and prepared defenses against the invaders.

Four years later...

Though the Gate is still open and the Neighbors still come through, most of the city's population has chosen to remain. Perhaps due to their faith in Border, the regular explosions and flashes hardly even faze the people living in Mikado City.

Outside the Forbidden Zone of Mikado City, a Border squad stood atop and around three fallen Marmods. Their expressions were carefree or uncaring about the mild destruction around them. They wore similarly styled outfits consisting of a long-sleeved, gray jacket and loose pants. The three males there had their collars raised up, while the girl there had the ends of her collar bent outward.

They had been sent out to deal with the Neighbors who had come through the Gate that opened up. The end result was what someone would expect from this particular squad; holes in the ground, a few things cut up that were supposed to stay intact, and three beaten Neighbors. Thinking that this was something out of the ordinary would only bring multiple strange looks from others.

The only girl standing there looked around at the three Marmods. She flipped her hair while speaking in a melodious tone that also gave off the feeling of a teasing older sister.

"That was honestly some of my best work yet. It's just a sad thing that Toby had to go and get in my way a few times."

"Did that even matter!? You still took the shot! If it wasn't for my reflexes, you would have made me Bail Out!"

A boy with brown hair underneath a trapper hat gave a scowl towards the girl.

She didn't even look in his direction.

Clicking his tongue, the trapper hat boy fixed his gray hat, which managed to cover his ears.

Ignoring what his two teammates were going on about, a boy with gray hair and a gray scarf looked over at their squad captain.

With a dull and flat tone that sounded like he could care less about what was going on around him, the boy asked, "Yuki-senpai, are you alright?"

The sickly-looking captain of theirs gave a kind smile towards the boy.

"Yeah. I'm fine."

Tsukiko Yuki was the oldest person there, yet he seemed rather young for an 18-year-old. The black hair that leaned towards the left had covered his onyx eye, but not the smile he wore.

"Take, you know that Yuki isn't so weak as to even get a scratch against these damn things."

Before anyone else could say anything, a soothing voice reached them through their earpieces.

Wisteria: "Calm down now. I'm sure Yuki-kun doesn't want to break up another fight. The last time he had to do that, he also had to write a letter of apology to the directors. So please, stop before I get the paper out."

"Yes, ma'am..."

None of them could see her, but all four of them knew that their Operator was giving a smile while nodding her head.

Wisteria: "By the way, you guys did well, and your teamwork is growing. You are really starting to earn your spot as a top tier team. At least by B-Rank standards."

"With a leader like Yuki, there's no way we're not great! Although that did sound a bit harsh, Mei. We've always been good enough for our spot."

Yuki said nothing. He gave a sheepish smile.

It was far too often that his squad would give unnecessary praise that most would find embarrassing.

"Don't you guys find it kind of weird that there have honestly been this many Gates opening up outside of the Forbidden Zone? A few a day is fine and all, but honestly, how many is that today? There has to be something up with it."

"I had asked some of the A-Rank agents about it, but they weren't really sure themselves," Yuki said. "Maybe Jin-san or Amō-kun would know."

"Well, they better figure it out soon! Like Suzume said, this is happening waaaaay too much! Yuki shouldn't have to use his off time for something like this!"

The trapper hat boy kicked the Neighbor as the scarf boy jumped down from it.

"Must you be so loud? We already know that Yuki-senpai has better stuff to do than this. He doesn't need you giving him a headache just because you're like some wild animal."

Three green orbs that had been floating lazily around his head started to dissipate until they were completely gone. The other three didn't seem surprised by the orbs in the slightest.

"It's not my fault that HQ isn't working faster. I mean, seriously, don't they know how fragile Yuki is? He already does more than enough when he's on duty, they shouldn't make him do extra when he's off the clock."

"They are trying their hardest, I'm sure. But I do agree they should hurry up before Yuki-senpai's body gives out."

The other two looked on as the Attacker and Shooter's argument went on. One watched with a sheepish smile, and the other watched with an irritated expression. They both knew this argument was pointless and almost daily, but they also knew they could only do so much about it.

Misaki Suzumebachi - the melodious girl - sighed as she shook her head.

Quickly getting tired of the argument, she turned to her captain and asked, "Can I just hit them now? We both honestly know this will go on for the rest of the day."

Wisteria: "You should let her. It makes things easier for us all."

"Don't you honestly find it a little insulting that they're saying you're basically so weak that you need protection? We all know that you're better than any one of us."

"It's fine. Those two don't mean any harm. Besides, I'm only really strong when I'm in this body. Out of it... I might as well be in bed with a bowl of soup next to me. Thank you anyway, Suzu-chan."

"Don't you have any pride as a man? I mean, you are the oldest of the four of us, and they treat you as if you were a kid." She let out a small sigh and shook her head. "I suppose my breath is just honestly being wasted on you, though. Whatever. They at least give me some good material."

Yuki only smiled an apologetic smile at her.

"You're honestly too nice most of the time, Yuki-san."

Seeming to be fine with that, Yuki looked over at his two arguing teammates. He gave them a fond look but said nothing.

Seeing the look they were getting, Kotowari Takeshi - the scarf boy - turned away from his argument to ask a question.

"Now that I think about it, we haven't reported back to HQ yet, right?"

Wisteria: "It's fine. While you all were talking, I took the liberty of sending in the report. They said you were all free to go. I still have some work to do, so I'll be staying over here."

"Try not to go overboard, Mei-chan."

Wisteria: "I should be telling you that. Either way, don't worry. I promised someone that I would treat them later on. I'll see you guys later."

.

There was a bit of silence between them all as they waited for a while for other agents to come and pick up the fallen Neighbors.

The two who had been previously arguing easily got out of their Trion bodies.

Suzume huffed as she turned off her Trigger and flipped her hair.

"That person is either Kako-san or Kō-san."

Toby Awdry fixed his gray trapper hat.

"Maybe it's both. She's on really good terms with both squads, so it wouldn't be surprising if both squads actually went along."

Takeshi brought up his gray scarf to shield himself from the breeze that passed by him.

"Says the one who always tries to invite Kusakabe, Shor, and Arashiyama squads for lunch every week."

"Shut up, asshole! So what if I'm more social than you? Just leave me alone."

"But if any one of us seems closest to others, it's honestly Yuki-san."

"Yeah. Now that you mention it..."

Yuki gave a small chuckle as his squad continued to walk away.

He enjoyed being around them when he was able to leave his house. There was never any malice coming from them when they talked about him. It always felt more like he was watching three children talk like they were grown people.

He could easily remember when he had met all of them and let out a satisfied sigh at the fond memories. They had always taken care of him when he was not able to do much, and he always cared about their well-being when they were having their own troubles.

They're always entertaining to be around as well.

Tsukiko Yuki was happy.

It was the beginning of the day, and he was feeling well enough to go out instead of staying in bed and feeling down.

After a certain incident, Yuki's body started to deteriorate at a rapid pace, leaving him with the side effect of having to stay in bed for a good portion of his days. If not for Triggers being something he could use, he would not have been able to move much. They were helpful, but the thought of needing them like this had always bothered him.

That did not mean he would not try to live his life.

He let out a silent sigh as he walked through the street and received multiple greetings from the other people.

Being the person he was, he returned all of them.

"It's nice to be out. But it looks like everyone's worrying again."

"That's not too shocking. You are quite popular for being a Border agent and just for being so... kind."

Yuki turned to see a beautiful girl with black hair cut short walking next to him as she gave her own greetings to some people.

She gave a proper greeting to him as well.

Her voice was a soothing one that mothers usually have when speaking to their children. That may have been why he was always happy to hear it.

She was Takato Mei - Tsukiko Squad's Ultimate Operator.

It was nothing new to see the two together.

They had known each other for a little over a year and had created the current Tsukiko Squad together. Beyond that, their homes had not been too far from each other.

The two walked through their neighborhood with no particular place in mind.

While he got entertainment from the other three agents in his team, he enjoyed the calming nature of their Operator from time to time. She was only a year older than him, yet he was grateful for all the help he had received from her before.

"Have you heard about what happened?"

"It's a possibility I have."

"Apparently, there was another attack yesterday. This time it was a middle school, and a C-Rank agent took down two Marmods. Kitora also took down some kind of new Neighbor. I guess that's to be expected of an A-Rank agent."

"That really is amazing. I know how strong Kitora is, so that isn't really shocking. But a C-Rank agent beating two Marmods is quite amazing as well. Well, I can tell a lie when I hear it. Also, I find it kind of funny that you speak like that about A-Ranks."

"Oh yeah. Jin was also at HQ yesterday." Mei let out a huff and grumbled. "He's the same as always. A good punch keeps him at bay."

"He probably doesn't mean anything by it. Besides, you're really pretty, so I'm sure any guy would want to just be around you. You can't really blame him."

That was when it happened. One of the worst possible things that could ever happen when Takato Mei was involved almost did.

She got a blush on her cheeks.

Noticing what he said, Yuki got ready for at least a headbutt.

He tried to quickly cover it up.

"O-oh yeah! Oh yeah! It's really nice that you get along so well with him! I th-thought you two would be at odds! Glad I was wrong! Hahaha..."

"..."

Mei let out a sigh.

"Yeah... Well... We have a bit in common. Besides you, he kind of understands what's going on."

"Is that so... Oh! Maybe we could all drop by Tamakoma later on! I'm sure Konami would like to talk to you and Suzu! Besides! I still need to teach Karasuma a thing or two! It's easy to trick Konami, but we're still working on Reiji-san!"

Yuki sighed as he put a hand on his heart.

Being sick was bad enough. Having this girl get embarrassed was something he would rather avoid at all costs. He did not want to die due to severe injuries or a heart attack.

.

With that crisis averted, the two continued on with their walk.

They had known each other for quite some time now. They knew each other best, and knew what the other would be thinking most times. They were also seen by others as some of the only people who could keep Tsukiko Squad in line.

"So, are you and Jin still trying to find a way around everything?"

"Always. Until we find the perfect way to help you... We will continue to keep track of everything. You might not think this is all worth it, but we do."

"Alright, alright. I'm not going to stop you two. All I will say is that there really isn't that much of an issue. If it does come down to that, I'm fine with whatever. The only ones that will really care too much are those three: you and Kō. Even then, I'm sure you all can get over it rather quickly."

"I really will punch you."

"Sorry, sor-"

Their conversation had ended up being cut short by the sound of a scream. Yuki and Mei looked at each other before making their way over to where they heard the scream.

They wasted no time in finding out what was wrong.

.

Once they had reached the location of the scream, they came across a group gathered in the area's park.

After showing themselves, the crowd quickly moved out of the way to allow the two to get through.

What they saw had them confused.

It was a small, six-legged robot-like creature.

Just as Yuki was going to grab it, the robot-like creature backed away.

A Gate started to open above it.

Before it could fully form, the creature was stabbed and fell to the ground.

At that time, a voice came through to Yuki that said,

Netsuki: "Attention, all Border agents! There has been an infestation of a new kind of Neighbor! You are all to find every one of these new Neighbors and destroy them!"

Then a man appeared on most of the crowd's phones. He held up a picture of the creature and spoke, "Border has found the reason for the Gates opening in the city. These are small Neighbors. Border is exterminating them right now. If you see one, contact Border at once!"

Yuki turned to Mei and saw her eyes looking more dull than they were a few seconds ago.

He knew exactly what was going on and let out a small sigh while standing straight up.

"So that's how it is... Looks like we're going to be busy today."

Yuki turned toward the whispering crowd behind him and clapped his hands.

"Alright, everyone! As Netsuki-san had just said on your devices, if you find any more of these small Neighbors, contact a Border agent, and someone will be there as quickly as they can! I will be leaving to help with the search, but I will make sure to get rid of any in this area!"

The crowd started to disperse as Yuki let out a small sigh and turned to Mei.

He gave a small smile and a mock salute before quickly leaving to search for any of the new Neighbors.

After searching the whole day, all the small Neighbors were dealt with, and every agent was now relaxing from the long search. They had gotten some help here and there from civilians, which did make things easier for them, but it was still difficult to find all of them.

The small Neighbors had been small enough to fit in places like a sewer drain or under houses, so having to find them by sight alone was troublesome. Even with the trouble, Border had been able to get a better reading on where they had been and made things go by much quicker.

Now that all was said and done, Yuki happily stretched his arms as he walked around.

"Looks like we've got them all. Man, that was a good workout. Too bad this doesn't affect my real body. I would love it if I could feel it afterwards. Getting in real exercise recently has been so hard."

Yuki himself had met up with his squad a little after the announcement and had quickly disposed of a number of the small Neighbors.

They were easy enough to take out. One hit from a simple Trigger was all it took to take them down.

They were rather weak overall.

"Sometimes it just feels nice to have things quiet around me. Minoru's not wrong when he calls them puppies. Still, they don't mean any harm. At least I get some breaks like this anyway."

It had been rather difficult to get away from his squad when they worried constantly about him and his health.

It had not just been his team. Others he had passed by had asked if he was feeling all right.

He had been a bit annoyed by the attention, but let it go as easily.

"At least we can all take a break now. Maybe I could go get some ice cream later on with Akane and Yoshi."

Easy days like these would make anyone have simple thoughts like this.

It was always a relief to know that calm moments like this were able to be had when things could get hectic at any moment due to the Gates opening around Mikado City.

Still... Things like today can cause issues later on. Jin is the one who can see the future, and I'm sure he only wants us to go down the best path. Even so, he can't control everything at once. Those spots need to be filled with improvisation by the rest of us. It can cause some delay in how things go and won't work out every time. Peaceful days are nice, but I need to be on guard when it matters.

Even if one person is having a good day, it may be hell for another. Yuki had always known this, so thinking about these kinds of things was important to him.

He let out a sigh before shaking his head.

"I need to stop that. It's making me sound like those two..."

He could only clench his fists and look up with determination.

There was only one thing to do at times like these.

"Let's go get that ice cream!"

"I've been told to keep you away from ice cream for a while."

.

Turning around, Yuki saw a guy in a semi-strange uniform consisting of a hoodie under what looked to be a yukata top and pants that had knots at the ankles as well as just above the knees. The person's actual appearance was that of a boy who was a year or so younger than Yuki, although taller than Yuki, with heterochromatic red and blue eyes. His hair was as black as Yuki's, but he had the tips of his hair dyed white.

"Hm? I don't see your squad anywhere."

"Heh heh... Yeah. I was able to escape them for the time being... What about you, Shiro? Where's your squad? They're just as persistent as mine when it comes to being around their captain. I'm a bit surprised."

"Oh! Kirai-kun went off somewhere. Hitsu-chan followed after him. She probably wants to make sure he doesn't cause any trouble for me."

"Ah... He probably went to 'gather more information', right?"

"Yeah... You're probably right."

"Well, if he ever quits Border, he can become a great informant. Although I'm sure that even then people would not want to be around him."

Letting out a laugh, the two continued to walk.

Hogo Oshiro had been someone Yuki found himself getting close to without realizing it at first. The two had similar appearances, but the people who knew them best were aware just how different they were.

Those differences were what kept them from working together for the most part.

Even so, calming moments like these were not rare for the two who thought of each other as brothers.

Their differences had not affected their interactions, and fights had never broken out because of them.

That was why they did not hesitate when hearing a nearby voice.

"Because there's someone you want to help?"

They both looked over and saw an Elite S-Rank Agent talking with a C-Rank agent wearing glasses, a young-looking boy with white hair, and some sort of machine-like object.

They both knew who the S-Rank was, but the others were new faces.

Deciding that there was no harm in it, they went over to greet the small group and introduce themselves.

.

Jin Yūichi grinned as he spoke to the ones in front of him. He looked towards the one with glasses on, but knew that the other two were paying just as much attention.

He had decided to ask a rather simple question in order to gauge their reactions.

Sadly, the answer never came, as someone had called out to him from the distance.

"Jin-san, hello!"

Having seen them walk up to them, Jin thought nothing of Yuki and Oshiro's appearance.

Even so, he knew how the people behind him were reacting.

Both boys behind him shifted their positions to hide something behind them.

"Oh, hey, Yuki. Hogo. Are you feeling well enough to be out right now?" Jin asked with less worry and more curiosity in his voice.

He did nothing to hide the glint in his eye.

Yuki had mentioned before how that sort of thing would happen when he was around Mei.

Lying to Yuki would not have ended well, so he had always just gone with it.

This time, Yuki seemed to think nothing of it.

"Yes. I am feeling fine right now."

"Must suck that you had to search with us when you finally felt fine."

"Not really. I got the chance to get out and move, so this is no problem for me. By the way…"

Yuki trailed off as he looked at the two behind Jin with a curious expression.

"If I may ask…"

Of course he would be interested in the boys being less than subtle behind him.

Jin kept a grin on his face, already knowing that one of the two behind him had already been sizing the two up.

"Right. Guys, these two are Mikumo Osamu and Kuga Yūma. The one behind Yūma is Replica-sensei."

Jin noticed the shocked and questioning looks he got from the two behind him, so he turned to them with his grin in place.

There was no reason for them to be wary of the two who had just come onto the scene, and he showed it in his expression.

Yuki also noticed their reactions. He said nothing about it in case the wrong words came out.

"No need to worry about these two. The only bias they ever really show is towards very specific things. They also keep secrets rather well."

"Hello, Mikumo-kun, Kuga-kun, Replica-sensei," Yuki said with a low bow.

The three gave their own greetings in response to the formality they saw. The two in front of them were their seniors, meaning they showed the right amount of respect from the start.

"So Jin-san, were you the one to figure out that these things were the cause of the Gates?"

"Nope. It was Megane-kun here. He's a C-Rank rookie right now, but he'll probably be moved up to B-Rank like you guys after this."

"Really? Then, if you need anything, you can just ask, Mikumo-kun. We're always happy to help."

"Right."

"Hey, they're like you then, Osamu. You are people who can't help but to...help."

Jin was acutely aware of the look he had been getting from Yuki the entire time.

His words had clearly kept things out, but there was one helping that at the moment.

Ah. I just wish he wasn't so intuitive when it comes to words. It would make my life just that much easier.

It had not been the first time that he had been found out for chasing his words too carefully.

Every time words left this mouth around Yuki, they were discovered.

But instead of continuing that line, he tactfully chose to change subjects.

"While we're talking about moving up in the ranks. Yuki, when are you planning on joining the A-Ranks? I've been hearing that complaints are piling up because of you. Some from Ikomacchi and others from Tachikawa-san."

"That's the first I've heard of it. They have been talking to me personally, but this is the first time I've heard that they were complaining to others about it. That's actually my fault then..."

"Is that so?"

It seemed that he had not been the only one wanting to keep things from others.

Watching Yuki subtlety shift his feet had been enough to tell him all he needed.

"Is there something you want to ask, Mikumo-kun?"

"I was just thinking that you must be strong if Jin-san and others want you to become A-Rank so badly. If I hadn't heard you guys talking just now, I would have assumed that you were already at their level."

"Ah... Hahaha. That's rather flattering. But those guys just want to mess with me, really. I am no better than any other B-Rank. They tend to get overexcited with these kinds of things. That's all there is to it. Nothing more and nothing less."

"Always the modest type, huh?"

Jin put an arm around Yuki's shoulder and started talking to the other three again.

"This guy is strong, when he wants to be. He could easily be an A-Rank and go toe-to-toe with some of the best. He doesn't take the offer though because he wants to go to A-Rank with his whole squad."

"Jin-san, you're exaggerating. I would quickly lose if I fought against an A-Rank. And I don't take the offer because I know I'm not strong enough to be A-Rank."

"Ah~ That silver tongue you have-"

"Jin."

.

Kuga looked between Jin and Yuki with his head tilted to the side a bit.

The words that the two were saying came out clear as day, yet there was something wrong with their conversation.

Jin spoke only the truth when it came to Yuki; there were no gray areas and nothing was false. Those words were countered by nothing but gray from Yuki. He spoke in a way that made it hard for him to tell exactly what was true and what were lies.

"Well, Kuga? Which one is telling the truth?" Osamu whispered, looking down at him.

That was the question he was still trying to answer.

The easy answer was to say that Jin was the one speaking the truth, but that did not feel right. Giving that answer would be saying that what Yuki was saying was nothing but hollow words to keep others from knowing the truth.

Except his words also held truth in them.

Deciding that he would just keep that to himself, Kuga said nothing particular and gave a half-hearted answer. It was the best course of action.

He was rather glad once he heard the next words that came from Jin.

"You two should probably be getting back to your teams before they start harassing the other agents for information on where you are. I'm sure you guys didn't forget what happened last time."

"True… Anyways. It was a pleasure to meet you three. If you need anything, don't be hesitant to ask. If you need anything at all, Jin-san can just tell you where our rooms are."

Kuga and Mikumo nodded while watching the two older males start to walk away.

Once they were outside of hearing distance, Kuga turned to Jin. His face had a relaxed expression while talking to the S-Rank agent.

There was no harm in asking what he wanted.

"Jin-san, what exactly—"

"Hm~ Sorry. I can't tell you guys anything about that guy. Like I said before, he's good at hiding secrets. I might accidentally tell you something completely false since I don't know everything."

That had only led to even more questions.