This is melancholy, almost surprisingly so.  It's also a bit hard to believe to me.  Spending the better part of their middle school lives fighting XANA should have created strong bonds bewtween the group.  After all, they have shared some life-defining moments together.  Yumi leaving was a sort of catalyst for the rest of the group to fragment, especially Ulrich.  I don't get, though, why Odd, Jeremie, and Aelita couldn't stay close-knit, even after graduation.  Maybe address their long-distance relationships in a follow-up, perhaps?  Anyway, I liked the story overall.  I like most any story in the CL universe with a darker tinge to it, but your writing always rings true.