Disclaimer: not mine and no profit is being made.
Matt was playing on his gameboy when Mello first walked in. Tetris, even now he remembers that. He was in the middle of a phase when he was obsessed with the game and beating first everyone else, then himself at the game over and over. He looked up as he always did when a new arrival came, vainly hoping that there might finally be another gamer at Wammy's house.
A quick flicker of the eyes, up and down, no console, no callouses from pressing buttons. That was that, Matt had decided looking back at his gameboy only to realise he had just lost. Another epic fail, a complete K.O. Loser flashed across his mind and Matt decided that he wasn't going to talk to the new kid, they weren't anything special. Just another non-gamer for him to ignore. Then something struck his gameboy sending it out of his hands to clatter on the floor. That had caught his attention. Mello, not that he had known the name back then, looked good. Amazing, for some stupid moment Matt thought he looked like an angel. No human had ever managed to look anything but orange through his goggles; Mello glowed.
Her (his, Matt knows better now) hair glowed like something really beautiful that Matt didn't know the word for. She (he) was special.
"You're really pretty."
It had been a compliment, but no one called Mello pretty. Mello was more breathtakingly beautiful than pretty, but that wasn't the reason. Mello's fist slammed into his face and it was then that Matt decided he was in love. He didn't know what being in love meant exactly, but he was, with the extraordinary girl (boy) that had just hit him. Then Mello had stood over him, not in a concerned way, or a triumphant way, more in an I-hope-he-isn't-dead-because-I-really-don't-want-to-get-punished sort of way.
Roger started fussing, and Mello, after figuring out that Matt wasn't actually hurt that badly, or maybe just getting bored, stalked off. Matt followed and that set the pattern for years to come.