Tonari no Oneesan ga Hentai de Doushiyou!?

Jun, a young boy, is left alone for a few days while his father works offsite. He gets the chance to sleep over at the house of Chisato, the college girl who lives next door. Jun has long harbored a secret interest in her, and now he finally has the opportunity to see her bedroom firsthand. As he explores the room, he notices a strange, unfamiliar object. Curious, he asks Chisato what it is and how it works. She smiles and decides to teach him, initiating him into a world of adult pleasures. What starts as innocent curiosity quickly turns into a passionate and educational encounter between the two neighbors, blurring the lines between childhood and adulthood.