After accidentally slapping her stepson, Yu's stepmother apologizes in the best way possible. As Ryota's father remarried Yu, Ryota gained a stepmother. Ryota is at the age of exploring 'physiological' issues, and his stepmother is incredibly beautiful, seductive, her smile seems to want to steal his soul. However, Yu is his father's wife, so Ryota gives up, knowing his feelings will not be reciprocated. Unexpectedly, an opportunity arises for him. His father will be on a business trip for three days, Ryota will not miss this one chance! He immediately attacks Yu to claim her! But Yu resists strongly and slaps him. Realizing he may have overreacted, Yu visits Ryota's room that night to make amends. Ryota agrees to forgive Yu on one condition, she must close her eyes. And he uses this opportunity to claim her once again! But unlike the previous time, this time Yu resists less, seemingly allowing Ryota to take over her body. The pleasure Ryota brings quickly conquers her. Although knowing this is wrong, Yu can't stop. She wants Ryota to fuck her even more. The two continue to have sex throughout the time his father is away on a business trip, even after he returns, they maintain this forbidden relationship of theirs...