High school student Koguma has no parents, friends, or hobbies and lives a monotonous life. When she buys a used Super Cub at her local bike shop, she finds herself having adventures and making friends.

When Koguma lets it slip in class that she owns a motorbike, she attracts the attention of one of the girls who sits nearby. Reiko insists on seeing Koguma's Cub, and proudly shows off her own.

Koguma adjusts to life with her Cub and expresses interest in Reiko's luggage case. Reiko makes a call and they stop by a credit union after school.

Koguma plans to spend the summer holiday working for the school, shuttling papers back and forth to a high school in Kofu. She finds herself learning more about maintaining her Cub.

Koguma visits Reiko at home, and the two have dinner together. Reiko recounts how she took a job at the Mountain Hut Kikuya over the summer as a means to pursue her own dream.

Koguma comes down with a fever the night before the class excursion to Kamakura and must cancel. When her fever is gone the next morning, she makes the bold decision to hop on her Cub and catch up with her classmates.