Koguma, a shy 2nd-year student in high school with no parents, no money, no friends, and no goals for the future decides one day to shop for a motorbike. When she buys an inexpensive used Honda Super Cub, it leads to events that will change her life.

When Koguma lets it slip in class that she owns a motorbike, she attracts the attention of Reiko, one of the girls who sits near her. Reiko insists on seeing Koguma's Cub, as well as showing off her own, and is pleased to meet a fellow Cub rider.

As Koguma slowly adjusts to life with her Cub, she mentions to Reiko that her luggage case seems convenient, so Reiko makes a call. After school, the pair visit a credit union, where the manager has an old Cub with a luggage case available to them.

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

With the arrival of autumn, Koguma and Reiko's attention turns to getting ready for winter. When the class culture festival committee runs into a snag getting what they need for their activity, the pair volunteer to use their Cubs to come to the rescue.

Shii invites Koguma and Reiko over to her family's shop for coffee, to allow her father to thank them for their help with the culture festival. The girls continue to look for ways to prepare for riding their Cubs during the upcoming winter months.