Starting with "Good morning, big brother♪", your cute little sister Chigusa and you have a sexy and radical brother-sister life. Chigusa, who is popular with the boys in her class, consults her big brother about his confession. In reality, she wants to convey her love for her big brother, so she tries every trick in the book to tease you. Chigusa, who is at a mature age, seems to know the secret to making your penis grow. Wanting to please him even more, she shows him her slit and pushes against him until it goes right in! She gradually starts to feel good too... and a lot of white stuff comes out!