they did in the raws
i think cos the seme was being too difficult thats why
I think it's because the seme gets jealous (when the uke is around girls). He does not know how to process jealousy well, so he starts acting distant and cruel to the uke. He wants to hurt him the way he thinks the uke hurt him. So, basically they broke up because of jealousy, fear, immaturity, and lack of communication-- due to the seme.
I read the raws too and...now I don't know if I wanna finish the story... Why couldn't they just talk about the jealousy...Instead he....I can't believe he did what he did to him.
I hope they address the reason they broke up, because Taichi was sort of a dick, I want more angst ! All the angst.