The story is narrated in the first-person by a sentient sphere, often referred to as the ball. The novel opens with the ball coming back to the living world in the form of a memory; the result of a monthly ritual in Brazil where the citizens remember the dead. As a memory, the ball tells its life story, which revolves around several main characters.

A young boy, Kazumasa Ishimaru, plays on the shore of a beach in Japan. A thunderbolt strikes the water, throwing debris everywhere and striking the boy in the head. The object that hit Kazumasa—the ball—now perpetually hovers above his head. Kazumasa’s mother worries how others will react to Kazumasa’s strange new condition. Kazumasa, on the other hand, takes comfort in the ball’s orbit around him. As the years pass, others in Kazumasa’s town come to accept the sphere, and he lives a happy childhood.

Kazumasa graduates high school and gets a job working for the railway system in Japan. He begins as a lowly ticket attendant, but he soon discovers the ball can detect deteriorating rails on the track. He is promoted to “Superintendent of Track Maintenance and Repairs” (6) and travels across Japan, saving countless lives with his special ability.