"By the way, this may appear to have a happy ending, but I realised later that it really doesn't. None of their problems are resolved."
So says the author, in the afterword. It's a little bitter, but it's such a refreshingly frank way to look at it that I end up liking both the story and the author that much more.
Dunno. "None" is the wrong term here. In the end Ito did start inviting Hatoko out, and stopped pushing her away (even if she thought pushing her away was for the better). And all of the problems are on Ito...Hatoko has a future plan and is invested completely in the relationship.
So I think the author was a little short-sighted on that quote. There are issues to work out, but this is, more than anything, a hopeful ending.