I don’t think they’re trying to create anything permanent. When they picked out this guy from the list didn’t they refer to him as the “next” one? That indicates he won’t be the last doesn’t it?
I mean, isn't that because he 'failed' at becoming an ideal stepfather or so/perfect choice, b/c other than being some kinda 'killer widow'/gold digger, it'd be easier to just use hookup apps if pregnancy was the goal versus a new 'family' (considering marriage is a huge commitment in a country like japan, if not just because of 'paperwork'/a paper trail unless somehow they also changed their identities too but i don't think they'd have that much resource/money to do so versus some kinda underground connection, tho anything's possible given that this is fictional
...Tho it would be fascinating to see this in live action but underage aspect aside, i imagine some live action series would avoid the incest aspect even if it's just a 'stepparent', even if there are some ridiculous anime/manga concepts that gets a jdrama series too. or if they just changed some aspects and make the daughter college age/last year of high school versus like 15-16 or whatever age she is)
I guess we'll have to wait and see. be interesting to see how far the author planned ahead if they didn't write themselves into a corner and just ends up with a bs ending, their other series are ongoing right now, so we don't know if the author prefers 'happy endings' versus sad/fucked up/bittersweet ones