A horror adventure novel that stimulates the imagination. What do you pray for with a thousand cranes? Senbazuru is generally known to be folded for "prayer". However, it is said that it has the aspect of a kind of obsession and a desperate wish... The main character "Yuichi Sasaki" is an ordinary 26-year-old office worker. One morning, Yuichi receives a call from a hospital called Tsukumo General Hospital, which he had never heard of. It seems that his lover Mayuri was transported the night before. He hurried to Tsukumo General Hospital, but... A scenario where you can't predict what happens next, a branching system with "cards" that determines the future of the story. Let's complete various stories surrounding Yuichi and Mayuri.