
The whole story between Hajime/Momo/Hajime's sister hasn't been revealed yet, so I don't know if Hajime had feelings before/during/after Momo's and her sister's relationship, but just speaking as someone who has siblings as well, my sibling's ex would always be off-limits to me, even if I had feelings for them first; I would just be uncomfortable dating the person my sibling loved, especially if it wasn't even a break-up but a tragic end like theirs.
But if you would prefer them to end up together, that's valid as well! I was just commenting my personal opinion.

Ofc each to their own. I personally dont see myself in them. It adds to drama ...falling in love only for her to be with your sister. You give up but circumstances brings you in each other's need. You know its wrong but being with her all the time and not falling love all over again is impossible but cutting her off is also not possible. I am a sucker for the angst
Probably an unpopular opinion, but I really don't want Momo and Hajime to end up together, it's a bit awkward dating your dead sister's girlfriend.
I still don't like Miki and I hate how much Japanese authors normalise incest and turn sibling love into something perverse.