Mimi Tachikawa and Yamato Ishida

Throughout Digimon seasons 1 and 2, we see limited interaction between these 2 characters, yet in spite of that and lack of hard evidence, there was something about that two characters that captured the heart of many fans, compelled us to believe that they were meant to be together. I can not speak for other fans (though I certainly welcome your opinions), but these are the reasons why I believed:

The "masks" they wear.

Matt acts cold and distant, while Mimi plays up to her spoiled princess role, while really, deep down inside, they're hoping for someone who can truly understand them. Also, they seem to have this mutual connection to each other. Remember that time when Mimi said she was tired of fighting? Who was the one that stood by her side? Not Sora, her "best friend", but Matt, the lone-wolf who'd pick on her from time to time. Maybe because he, too, was tired to fighting. But as an old brother and a co-leader (or at least I'd like to assume), he had to be strong for the team. However, when Matt found out that TK was no longer dependent of him, he left the group (sick of fighting I guess). Mimi then immediately followed his footsteps. This is interesting, because if she wanted to leave, she could have left a LONG time ago. Why right after Matt? Reason is that she felt a reason to fight when Matt was still part of the group. Remember why her crest glowed? Because she wanted to protect those she loved. Now with Matt gone, she, too, lost her reason to fight.

They are always standing/sitting next to each other.

No, this is NOT a lame excuse. Why do the animators place them near each other ALL the time, if they were not going to be together? If you look at this from a realistic point of view, wouldn't you want to be close to someone you like? Just like how Matt is always by TK's side, it's the same thing. This won't make much sense until you read the LAST reason.

The way Matt talks to Mimi.

I know they hardly talk, but when they do, you find that Matt is always making comments, not rude, just small, harmless comments about Mimi. He doesn't hate Mimi, or else he wouldn't have stood up his best friend Tai for her, but rather, he doesn't know how to talk to her. Why? Because he has different feelings towards her, something more than friends. That's why he can talk to Sora with ease, because they're friends. Just friends. While in Mimi's case, it's different. Remember, he was never too open to other people, never mind girls, and suddenly, this girl he likes is with him 24/7, of course he's at a loss. Take a looks at the reality world. Isn't that what most guys do to girls he likes? Don't forget the age factor. He's what, 11? According to Freud's psychosexuals stages, this is when the guys run away from girls because they think they have "cooties"(and vice versa). I guess Sora was just too tomboyish for Matt to think she had girl-cooties.

Mimi is just like TK.

We all know TK is the single most important person to Matt. Matt adores him not only because he's his brother, but because he's so young, pure/innocent, and weak (relatively). It's a guy's thing to want to protect the weaker ones of the group, and besides TK, the youngest and weakest one would have to be Mimi. But that's not all of it. Matt also sees TK's innocence, carefree, and happy characteristics on Mimi, which might even trigger Matt to want to protect Mimi more. It'd also create a sense of familiarity (because Mimi and TK are so alike), whereas Sora is the opposites of TK and more like Matt himself. Sora and Matt would make great friends, no doubt about that, but a good girlfriend? Not so sure.