I just want to point out that
In essence, A-Chan is agreeing to an arranged marriage with Koharu's father for the sake of Koharu and their unborn children, at the request of her future lover. Remember, this is a culture where arranged marriages are still a thing, they are just usually arranged by the parents, not your childhood friend whom you are going to move in with once your husband dies in an accident.
Just because it's common practice, it doesn't make bad thing any less bad. I'd even say it being arranged by your childhood friend and future lover makes it worse in fact.
Yap, and if you think about it…….Rin doesn’t die because for some reason A-chan needs the D and to pop not one child BIT TWO!!! way the hell does the idea of saving Rin is A-chane getting D and having children after????
This is the kind of yuri manga that I hate, and it makes the idea of Bisexual people exist as an plot only, give that is whay exactly happen! and I REALLY hate with the hetero part is used as an cheep plot drama and nothing else comes out of it!