sorry if this makes you feel uncomfortable but i want to ask you about a hentai that i have been looking for it for a long time but still can't find it so if you know about it i hope you can tell me

it's about a guy come back home to help his sister in law with the festival in the neighbour when she request, THEN SHE SAID SHE JUST ASK HIM BECAUSE SHE FEELS LONELY and many things happen he has sex with her and confess his love to her, then she asks him if he know why she doesn't change her name( because she didn't marry his brother, she love him from the start).
as i can remember 2 things more: his parents are dead, his brother may be is studying abroad.
so if you know anything about this such as the name or the author please tell me