碧ヶ淵 夜伽の村のお嫁様

Main character's mother dies, and relatives arrive for her funeral. That evening niece comes to his room and starts hugging. Due to special air in the room protagonist can not resist and robs her of virginity - that in addition to an affair with another relative he was having. Then comes the third girl, and all of them turn out to be bride candidates. Protagonist needs to live with the for seven days to determine the best bride for himself.

[From vndbreview]