i didnt read fully, but one thing for sure, at the end, turns out that the guy is blood related brother with the girl, thats why he destroy all the pictures and asked by the oldman to just leave ( the oldman realize that the girl fall in love with the guy )....in the last panel, the girl say that she will study hard and want to meet the guy at his town.
@Incauto Basically boy in abusive home falls for a girl. Turns out she is being porked. In revenge he porks their daughter but guy that likes her, sees it and gets mad and so the chain lengthens.....
Base +7, tomu-kun -6, Tomo the Graet -6, skeksis -6
When he was a kid, guy went out to follow where his mother went to find her seemingly being raped/NTR by the old man (the again it's DV dad so eh), and he plans to seduce the old man's daughter and spread the pictures to ruin him as revenge.
Then on the last day the old man came to have a talk with him. Roughly he starts with stating that he realized the guy is the woman's son (he used a different last name from the past, but it's his mother's maiden name) And how since the guy didn't bring it up he planned to also plays along and not mentions it. But the daughter seem to have fallen for him.
Then he tells him she has blood connection with him, that the girl is the old man and his mom's daughter, thus his half sibling.
:v Not sure of the conversation after that, but the final page have the floating text roughly saying it's better for him not to see her again or something like that.
EDIT: Just to note that Kureha calls the old man "ojii-san"(uncle) so I don't think she's registered as his daughter.
The mother was not being raped, though she was getting NTRd. The old man was trying to save the mother from an abusive drunkard husband and that the relationship was of love. It was just the MC misunderstanding the situation.
The MC felt a lot of pain after the realization of all he did.
The heroine in this story is indeed the MC's half-sister.