Father is about to get NTR'ed.
No sht
Well he let his daughter be named after her lesbian lover I think he would be okay with it.
It's possible he just didn't know about his spouse's ex or was okay with her naming her daughter after her dead ex.
Japan is hellbent on exploring every possible type of ship and I for one am happy to ride that imagination train and see all the stops, even if it gets cringey. The layers of awkwardness that can pile up in this story is dizzying:
1. The daughter gets jealous of her father's affection for her mother.
2. The mother feels like she is betraying her daughter by sleeping with her husband.
3. The father secretly monitors the mother and daughter being overly intimate over a period of months and begins a campaign to restore their morality through psychiatry, religious intervention, and finally legal action
4. The daughter grows up and brings girls home and drives mom insanely jealous (as a previous commenter mentioned)
5. The daughter remembers everything of her past life and cannot help exploit that information to manipulate the adults who were once her childhood friends by using their secrets against them (ok this turned dark for some reason).
The First Two are reminiscent of the Oedipus-Electra Complexes that have been prevalent in literature since Ancient Greece. Nothing really that new, for Japan to be exploring