Kino, a traveler who journeys the world with his talking motorcycle, Hermes, arrives in a country where people live inside massive domes. There, she meets a girl named Inertia, who asks him to deliver a letter to her pen pal—a boy who lives outside the dome.

In this prequel to the Kino no Tabi series, young Kino is being trained by their teacher. They learn how to ride their motorrad Hermes and develops their gift of excellent marksmanship. However, their guilt concerning the real Kino is with them when they decide to set off on a journey. All the while, Kino is becoming confused about their real identity.