Takuya Arima is a young student whose father, a historian who has conducted various researches, disappeared recently. During a summer vacation Takuya receives a peculiar package from his missing father, along with a letter containing information about the existence of various parallel worlds. At first Takuya doesn't take it seriously, but soon he realizes that he possesses a device that allows him to travel to alternate dimensions. Is his father alive, after all? If so, where is he?
Fourth dormitory of the Rat Production (commonly known as Nezumi-sou), the place were dropout idol girls live; the former child actor Sekino Roko, musician Nukui Hayu, and model Maehara Nina. Sakura Ino, who always dreamed of becoming an idol, moves in. At the same time the decision is made to demolish the dormitory. Due to the project launched by the manager Kajino Hoho, "Ochikobore Fruit Tart," occupants of the dormitory form a new idol group called "Fruit Tart," and start their activities in order to repay a one hundred million yen debt.
Third season of Yahari Ore no Seishun Love Comedy wa Machigatteiru.