I could have liked this ending if it were better paced. As it was, it had some interesting ideas that came out of nowhere and so seemed awkward or unfitting because we weren't allowed to see them actually happen.
I actually like having the high school couple break up, even if Tai and Futaba were cute, because that's realistic. People change and grow and you go to college and even if you end up at the same one, you see there are more options. Plus, they were very sweet in an infatuated way I'm not sure would have worked long term. If that was the biggest thing the ending did, I'd be fine with it. But it wasn't.
Masumi being bisexual is hmm. On one hand, I'm all for bi representation. On the other, her arc that seemed like it was trying to get across she was a lesbian, and while people can totally learn new things about themselves and change how they identify because we didn't get any hints of that in what we were shown, it seemed a little out of nowhere. If the story had explored it, I would have been super there for it, but because it didn't, it seemed tacked on. That's a reoccurring theme for the last chapters.
Touma and Tai getting together is another thing I could have liked if it was paced well, but as it is... I didn't necessarily read Tai as bi (or some form of not straight), even having been spoiled for the ending, but sometimes it takes a very long time to address aspects of your sexuality so him coming to that realization over seven years isn't that out there to me—except that again, we didn't get to see any of it. And since a lot of this manga is about change and your perception of others, the reasons I'm interested in Tai and Futaba having broken up seems like they should have prevented Tai and Touma from getting together—the ways people change over time and you can't really ever understand them, especially as they change, and that's especially true of childhood friends. And I feel like, with the writing of the rest of the manga, that it could have put my issues to rest if we were shown any of the process of them getting together. But, like everything in the epilogues, we weren't show that process. To us, it just happened.
I don't think you have to spoonfeed everything to your audience and show them absolutely everything.My favorite endings are somewhat ambiguous endings when they're done well. But a seven-year timeskip covered in one and a half chapters is probably a little too much a leap. It wasn't horrible, but people seven years in the future are going to be different from who they were seven years in the past, and so it's always a risk in jumping around like that without giving the time needed to establish things. Honestly, I think if they wanted that bittersweet ending, it should have been after Tai and Futaba broke up—actually show that scene and then the characters being friends and comforting each other afterward. Or show them meeting up for the first time after five years. But actually show those things instead of talking about them to skip on to a relationship that could work but as it is, is pretty out of nowhere. I think this is one of the only times in my life I've ever said "actually, as this is written now, I think the gay relationship becoming canon makes the ending weaker."