Mio Yunoki attends a school where both academics and sports are at a high level, and she spends busy but fun days with her childhood friend Rinka Ayukawa, who is the president of the student council, her cousin Yui Ikoma, and Konomi Asahina, a junior in the student council who adores her. spending time. Her parents are mainly active overseas, so they are rarely at her house, but she doesn't feel lonely because she has her live-in helper, Shiori Toya. She and Shiori consider each other like sisters, and they have a family-like relationship. Mio is living a fulfilling life. But one day, an unexpected misfortune befalls her.