Riku Watanabe, a 17-year-old known for her gentle and caring nature, has been a dedicated member of the student council since her sophomore year. She actively participates in community activities and strives to make a positive impact on those around her. Riku's kindness extends beyond her official roles; she consistently reaches out to help others, earning admiration and respect from peers and teachers alike.

However, Riku's life takes a dark turn when she unwittingly becomes the object of obsession for a fellow student. Shortly after meeting her, this individual becomes dangerously infatuated with Riku, his feelings escalating to the point of obsession.