Because it just FITS!! roze and blue, key and lock, Miki and Yoru :P Because Ikuto is the best to deal with Amu's obstinated character and Amu makes it easy for him to open his heart. And i must admit that the age difference and the opposite teams(Guardians/Easter) gives it a touch of forbidden that only makes it better.
Difference in age may be an obstacle for someone, but Amu no always be a child... Amu and Ikuto haven't secrets from each other, they don't pretend someone who they aren't. They understand each other. Amu is relaxed when she is with Ikuto. and all things which mention kamuly...
Tadase is a girly man, for one. Plus Ikuto is always teasing Amu, which is a SIGN!! Plus Ikuto is just freaking awesome and all that crap, and him and amu are like waaay alike that it'a not even funny. And who cares about age? Amu's gonna grow up, so what if Ikuto is like a pedo right now? (xDD) It just.... makes sense, okay? >:O?
