All I remember about the game which is Japanese the main character moves in with pregnant sister in law her husband who is also his brother had died , MC went to shrine to pray for her unborn child ( to be healthy) while at shrine he broke part of a Statue and did not tell anyone ,as a result he became cursed
being unable to eat regular food and only able to consume breast milk
he found this information after talking with SIL and both of them going to shrine to consult a priest
and must create a new life . SIL agrees to help him she has first child becomes pregnant curse is lifted
they get married I believe she was running a store or restaurant
not dark just a lot of sex and breast milk
possible her child had already been born been a while since I played