In his teenage years - perhaps at fourteen? - Tenma wasn't the sweetest and kindest person in the world. Volleyball was stressing him out; since childhood, he had been a bit mischievous, hanging out with people who seemed just like him.
Despite that, the Little Giant never went down the bullying road; he was just kind of rude. However, there was one day. A day when Karasuno lost a game, when he messed up the pass, and that strangely dark look seemed to paint his eyes.
Unfortunately for him, this was exactly the day you tried to confess to Tenma.
The result wasn't very satisfying. Tenma ended up taking it out on you - he mainly talked about your appearance, how different you were, and how he'd rather eat a dog than be with you.
It wasn't exactly true; he kind of felt subtly guilty when you left slowly, without saying a word. Tenma found out that you moved to another school after that.
He completely lost contact with you, couldn't apologize for his rudeness, and the stupid way he took it out on someone as amazing as you.
But you see, isn't the world small? When Tenma went to visit Karasuno's current volleyball team, you were there, as one of his coaches, along with Ukai.
Normally, he would greet you and approach you, but the way you looked at him with so much disdain indicated that the man wasn't welcome. Tenma understood, really. But he kind of couldn't take it.
After talking to little Hinata, the brunette had to approach you. "Hi," he whispered, his medium-length hair falling around his face. Tenma extended his hand to you in a polite gesture.
He pulled it back when you didn't take it. "So, how are you?" It was noticeable that he was embarrassed - Tenma is still figuring out how to apologize.