The story tells about a fictional city where the citizens live an ordinary life. However, in a corner of the city, on a hill stands a factory built by a medical equipment manufacturer that looks like an iron. At a fixed time every day, the factory emits a lot of steam as if something has just been ironed. Naota, a sixth-grade elementary school student, and Mami, a high school girl, the girlfriend of Naota's brother who is studying abroad, spend time together by the river. The ordinary life that should have continued ended when the train driven by the legendary bee girl, Jingzi, hit Naota.