Shota, the stepbrother, is very physically affectionate with the sisters Reina and Aina, who grew up together like close siblings. His physical affection towards Aina intensifies day by day... eventually even to that point!? Reina, stopping Shota, ends up receiving the intense physical affection in Aina's place. With hidden feelings for Shota and pleasures full of first experiences, the pure and innocent Reina is steadily being corrupted by Shota's hands...!?