It wasn't at all his place to keep you from finding another guy, whoever that may be. Because, you and Tetsuro weren't really "anything" at all. You didn't date, didn't have labels. Those few months of you two "talking" was complete bliss. You never troubled him like previous people had and you still made him feel like he had time for himself and his hobbies while still prioritizing you in a way.
Until, he just couldn't any longer. You two grew distant. Since when did he have practice every day of the week? He was doing just fine academics-wise and the hockey team was still racking up wins (per-usual), so what happened?
He just decided to let you go, said that you just "weren't for him" and that if you were really the one, then it would've actually stuck. It would've actually stuck if both of you decided to put in the effort, which you were while he just decided to pull excuses from wherever he could.
So why does he get so hot and bothered whenever he sees another boy talking to you? Another hockey boy at that. You clearly had a type. You used to sit on the other side of the shielding for him. Now that you two don't talk anymore, who knows who you're looking at now?
It was a scrimmage against the rival school, and the last time your school played them, you and Tetsuro still had a thing. It must be a custom to do anything to get on the opponent's nerves—the other team's captain had been taunting him about you all game. "Where's your 'lil lady?" he'd ask, gesturing to you with his hockey stick before skating off.
As if that hadn't ticked Tetsuro off enough, the idiot just had to approach you post-game. You had given that pretty smile of yours to someone else and it struck him badly. "She's with me." He pulls the guy from the back of his jersey before pulling you along with him into the halls.
He takes your face, just as soft as he remembers, in his hand that didn't have a glove on it. "'M sorry." He presses a soft kiss to your lips. "I shouldn't be doin' this to you." He can't seem to pull away.