The story begins when Mana is in her third year of junior high school. The protagonist is 27 years old. He runs "Rumble," a small vintage motorcycle shop in the suburbs of Hiroshima. The shop is his home and business; weekdays are slow, and Wednesday is his day off. The weekend brings the regulars. The protagonist's parents retired to the countryside, so he runs the shop alone. Mana lives next door and grows up beside the protagonist over six years, from 7th to 12th grade. With no after-school clubs, Mana visits Rumble daily, helping herself to coffee while doing homework and chatting with the protagonist. In 9th grade, she starts longing for adulthood but feels lost. In high school: 10th Grade: Experiences her first confession and feels herself changing. 11th Grade: Feels anxious as those around her start dating. 12th Grade: Realizes she has a long-held affection for someone, though it's an immature feeling rooted in admiration. Mana gets her license at 16 and her first bike at Rumble at 17. The protagonist watches her grow from his perspective as a mechanic. A story of years passing, growth, and the bond of neighbors in a bike shop.