Her younger sister, Rimu, is shy and quiet in front of her family, but she is actually curious about sex and has feelings for her brother Hajime. One day, Hajime is entrusted by his parents to stay home while he goes to a relative's funeral. Hajime, who was told his feelings for Rimu, once brushed it off, saying, "We're brothers," but he crosses the line when he is pressed, "It's okay to play, it's okay if it's just a physical relationship." - Then the two of them do H as if the tag has come off, and for two days without their parents, they go as their sexual desires go.