Not sure why we're spoilering since it's a series that was finished a while ago and isn't getting posted here.
In any case, I thought the ending itself made sense for Emi's character arc. I would have liked to see more of her learning more about the night life, the stuff Kei was teaching her remotely, her growth as a group leader and so forth, but what we got wasn't unsatisfying to me. It felt a little off on the first reading, but on successive reads it feels more natural, since I'm not going in expecting a different sort of story. Plus the little flashback-as-epilogue really does solidify how serious Kei's been about Emi all along.
I think the key really is re-reading it a few times. If I'd only read it once and walked away, I probably wouldn't like the story as much as I do.