its funny how such a wholesome manga has such ferocious discourse in the comments.
people are imperfect! both kase and yamada have jealousy issues, but both of them also seem to be slowly having character development at a realistic timescale. remember last time yamada got jealous, but then she calmed herself down looking at some flowers? that's development!
both of them are absolutely head over heels for each other, and it's not that fragile of a relationship, it's just a bumpier one because they're both only 18 or 19 and are still figuring out how to communicate healthily!