Shouta is very affectionate towards his sisters Rena and Aina, they grew up as close siblings. Day by day, he becomes more affectionate towards Aina… and eventually he even sneaks into her room at night!? Rena tries to stop Shouta, but ends up receiving his affection in Aina’s place. Due to her hidden feelings for Shouta and the pleasure of experiencing things for the first time, the once innocent Rena is steadily being trained by Shouta…!?

“I want you to fuck me like my big sis!” Aina discovers that her older sister Rena has become her brother Shouta’s sex pet. Unable to stand Reina monopolizing Shouta any longer, Aina finally sneaks into Shouta’s room at night…!? Using the techniques she learned by secretly watching him with Rena, she tries to take the lead — but as she experiences the real pleasure, Aina’s arousal only keeps growing! Alongside her sister Reina, Aina too is gradually trained and broken in…!