Although Fuutarou Uesugi is an exceptional high school student, his life is far from easy. His unsociable demeanor and solitary tendencies have left him with no friends, and his family is struggling to make ends meet due to his father's debt. During one lunch break, Uesugi gets into a dispute with a new female student over "his" seat, fueling animosity between the two. However, fate provides him with a chance to clear his family's debt when he is offered a lucrative private tutoring job for a wealthy client's daughter, Itsuki Nakano. The pay is an impressive five times the market rate, but Uesugi's excitement quickly turns to dread when he realizes that Itsuki is actually the same girl he had argued with earlier. Despite his attempts to make amends with Itsuki, Uesugi soon learns that his troubles are far from over. Itsuki and her four identical sisters - Miku, Yotsuba, Nino, and Ichika - all require his tutoring services, but they refuse to cooperate, despite the risk of failing. Nevertheless, Uesugi remains steadfast in his determination to change their attitudes towards studying and ensure their academic success, as his family's livelihood is at stake.