Hajimete no Orusuban

Based on the erotic game created by Zero, this light novel follows the lives of twin sisters Shiori and Saori, who share a quiet but intense infatuation with the young man living next door, whom they affectionately call "Onii-chan." Recently, the girls have begun developing a newfound curiosity about adult matters. Eager to explore these awakening feelings, they quietly resolve to have their beloved neighbor teach them everything they wish to know. When summer vacation finally arrives, an unexpected opportunity presents itself. The twins' mother asks the older boy next door to look after both the house and her daughters while she is away. With long, unstructured days stretching out before them and no parents around to supervise, the three are left entirely to their own devices. What begins as a simple house-sitting arrangement quickly transforms into something far more intimate, raising the question of just how thrilling a summer spent alone together can truly become.