I really like the writing in this series and how the high schoolers actually feel like high schoolers. It's a messy time where you're bound to make mistakes, your self confidence is at your lowest, and your selfconsciousness is at the highest. Seeing how all the characters make mistakes and how trying to fix them is a long and complicated process is so refreshing and engaging.
With Shima and Mitsumi I can go either way tbh but it all depends on Shima. It's clear my dude not over her and still likes her, but it's also clear that he's the one that needs to change. If he actually can mature and make sense of his emotions and insecurities, and actually demonstrate how deeply he cares for Mitsumi both to himself and to her, I'd be down with it. If he does all that and Mitsumi rejects him I'm still down. Hell even if he stays an emotional wreck it'd be sad to see but it'd still be a good story. The one thing that'd be bad imo is he doesn't change and still confesses again, but I don't think that's happening.