Kenta, a high school boy, ends up renting a room with his father's acquaintance due to certain circumstances. However, the rented room is the house where Yumi, a naughty older sister whom he once met when he was an elementary school student, lives. Kenta spends his days unable to stop being excited by the sight of Yumi, who is still as sexy as ever. Furthermore, I have a feeling that a suspicious interaction with Miko, a classmate of his who has spiritual powers, will begin... Kenta's struggles unique to adolescence are vividly depicted.