Japan has devised a complicated system known as "The Red Threads of Science" in a futuristic civilization to encourage successful marriages and offset declining birth rates. The government assigns marriage partners to young people at the age of 16 based on a compatibility calculation, with harsh consequences for those who defy the arrangement. Yukari Nejima, an adolescent who considers himself ordinary in every regard, believes that this method may be his greatest chance at living a satisfying life. Yukari, however, rejects the system and proclaims his love for his classmate and long-time sweetheart, Misaki Takasaki. Misaki, after some resistance, reciprocates his affections in a passionate encounter. Unfortunately, Yukari gets his marriage proposal before the two can continue their love.