Evidence

ep1: Tai said when he was introducing everyone"Thats Mimi, I bet u can guess her favorite color on the first try!" It was a kinda personal tone of voice. And did he say anything that personal with sora? (sarcastic) Oh wait let me think, Guess what? DON'T THINK SO!!!

When but scratching Sora made fun of Mimi's cutie hat, Tai said, "Now Now, her name is Mimi." You go Tai!

When Mimi screamed 4 help, Tai was like "MIMI MIMI! WHERE ARE YOU!!!" Major terror factor there.

ep2: When shellmon attacks and Mimi's almost hit, Tai yells out "WHATCH OUT!!!" Awww sweetie Taichi....

ep3: Mimi"I don't walk this much unless I'm in a mall, and as u can see we're no where near one."
Tai"Mimi stop whining."
Mimi"NO! My feet hurt!" Tai is always picking on her! Ever notice that! Oh c'mon! Little boy's usually go through this phase where they think flirting ends in the girl crying. Trust me I know, my little brother's going through that phase. I mean really! If they were in a different situation Tai woud be pulling her ponytails and snaping her bra 4 god's sake!

ep4: When they're at the yokomon village Tai says "What is this stuff?" Mimi"Be polite and just eat it, a gracious guest never insults his hosts cooking." Tai"I can't even tell if its cooked or not." LOVER'S SPAT LOVER'S SPAT!! I smell flirtation!

I'll get more evidence when I'm less lazy and Mrs. Evans gives us less homework. So basically your waiting 4 hell 2 freeze over.