Kaihei's life takes a drastic turn when he discovers that his deceased grandfather has designated him as the chairman of St. Luminous Mission High School - a school entirely comprised of female students. From being just an average high school pupil, Kaihei now has the task of managing regulations, events and disciplinary actions while adjusting to a new and unfamiliar environment. When he arrives, he finds out that one of his fellow students has gone missing. Without wanting to involve the authorities, Kaihei mobilizes his trusted companions to solve this mystery before their graduation.