Masaki doesn't know who his soulmate is, not for many years. He remembers the first time he felt his soulmate, a sharp stabbing pain that crushed his chest followed by a bone deep ache and weariness. It went on and off for days, getting worse and worse before letting up. He didn't realize it then but years later he would find out that his soulmate was experiencing extreme emotional pain not physical which is why it fluctuated so much, disappearing and reappearing seemingly randomly throughout the days and nights. Over time the pain lessened, not reappearing for days. And then came a different kind of pain, one that burned and left bruises that covered his hands, his arms, his torso. This physical pain came about randomly, sporadically, mostly around the time school let out. Masaki figures his soulmate must like to get in a lot of fights. He figures it must be a boy, no girl is dumb enough to get in this many fights in such a short frame of time.

When his dad remarries, Masaki does his best to accept his step-mom and step-brother, something that gets increasingly difficult as the pain in his chest doesn't dissipate. It's then when Hiroto comes home everyday with evidence of fist fights that Masaki, ever doubtful and hesitant, begins to put the pieces together. He refuses to believe it, thinking he's just being stupid. His brother can't possibly be his soulmate. But denying it becomes hard when everything begins to match up. He feels the pain from Hiroto almost daily fights, feels him suffer on the anniversary of his father's death.

All too soon, there are too many coincidences to make excuses for. He tracks Hiroto one day, following him after class. He watches as his brother fights and curses when he feels the pain match up to the blows he deals out and receives. After that, denying it is useless. Masaki still refuses to say anything. What would people think if they found out his soulmate is his brother!?

He does everything he can to keep Hiroto from noticing. Thankfully Takeru steps in, helping guide Hiroto and stop him from getting into so much trouble. Masaki is grateful because Hiroto never did listen to him when he tried. And he did try. Time and time again, going as far as to pull Hiroto out of fights and even jump in with him to end the fight quickly. But Hiroto only got mad at him for interfering, refusing his help and jumping into even worse fights to spite him. He wishes he could've slapped him upside the head and told him to knock it off for his soulmates sake. He would've too if Hiroto had shown any care for such a thing as soulmates. Which he didn't. Hiroto loudly protested the very idea, furious for reasons he wouldn't tell Masaki. Deep down, Masaki knows the real reason he won't say anything is not because they are brothers, they aren't related by blood anyway, but because Hiroto would never accept him. Hiroto wouldn't accept anyone as his soulmate but especially not Masaki.

Masaki resigns himself to a life with Hiroto as a platonic soulmate who doesn't even realize they're soulmates.

When their parents die, things change.

It's just them now.

Takeru and Masaki and Hiroto.

Masaki wouldn't do anything to jeopardize that. He was afraid if he had said something, Hiroto would reject him and he and Takeru would leave him. Takeru has always liked Hiroto more. If he had to choose, Masaki has no doubt of where his allegiance lies.

When their parents died, Hiroto was too caught up in his own pain to realize that some of what he's feeling isn't even his. Masaki will forever feel guilty for being thankful for that. He shouldn't have been grateful for anything on the day his parents died, on the day of their funeral; he's an awful son and a shitty human being for it but he can't help but feel grateful that Hiroto never seems to notice it. His brother, his soulmate, also never seems to realize it when the three of them start training, start going on jobs, start fighting together for real. Masaki thanks Kami that Hiroto has always been oblivious. Well that and always filled with rage that overpowers everything else he may be feeling. Hiroto charges into fights without thinking of his injuries, without thinking of his soulmate.

Masaki notices most of the injuries that appear on him from Hiroto, it is easy to distinguish what is his pain and what is his soulmate's echo after so many years.

Losing Aniki hurts more than anything else he or Hiroto has ever felt.

Before he realizes it, it's become just him and Hiroto.

Hiding everything from Hiroto becomes harder. His brother looks at him more and more strangely, more suspiciously, after fights after that. But he doesn't say anything.

Masaki feels both hurt and relieved for it.

It isn't until after the mess with Kuryu , when they are on a job together that things come to a head in one of the worst ways he could imagine.

The job was simple. Their client sent them to a warehouse to meet with a few members of some gang or another to exchange some hush money. All they had to do was give them the bag of cash and retrieve a flashdrive. Which they did. They just weren't expecting to get ambushed on the way back to the client with the flashdrive. It wasn't even a decent ambush, the men that came at them were clumsy, inexperienced which was why they brought a sniper. A sniper that neither one of them had known about until they shot Masaki.

Masaki had gone down like a rock for all of five seconds before getting his shit together and grabbing Hiroto and getting them the fuck out of there. Adrenal had been on their side and they managed to get far enough away before the pain and blood loss became too much. Luckily the bullet missed his vital organs, planning itself in his side without even hitting his ribs. Hiroto managed to get him to their underground doctor in time and Masaki was expected to make a full recovery.

Unfortunately it left Hiroto with a matching pain and wound that couldn't be denied. Masaki had known from the second he'd woken up and took one look at his brother. He had expected to be interrogated and promptly kicked to the curb immediately.

Instead Hiroto took him back to their apartment and gave him time to think while he finished their job, returning the flash drive now that he knew Masaki was okay. When he got back, Hiroto still didn't say anything, instead spending the day helping his brother to get around and taking care of him.

That night they settled in together, both feeling the pain of the bullet wound and waiting for the other to break the ice. Masaki was the first to speak, apologizing for keeping it a secret. Hiroto was understanding after hearing his reasons but expressed that he still would've liked to know sooner. They laughed over how oblivious he'd been for years before deciding to talk things over more in the morning; Masaki was obviously too tired to continue and passed out as soon as his head hit the pillow.

He knew when he woke up the next morning, Hiroto curled protectively around him, that everything would be okay.

(Hiroto made him wait until he was completely healed, no pain left for either of them to feel, before doing anything physical with him. Masaki both loved and hated him for it.)