Standing at the summit, Aoi Yukimura makes a promise with her childhood friend, Hinata Kuraue, to climb the mountain together again when they grow up. However, the two friends lose contact as the years pass, and after a playground accident, Aoi is left with a fear of heights.

Having shifted her interest toward indoor hobbies, Aoi is content to start high school at her own pace. Her expectations soon change when she reunites with Hinata, who quickly reminds Aoi of their promise. While Aoi is initially hesitant, a familiar scenery evokes memories of the mountaintop. Wanting to rediscover the pastime, Aoi agrees to join Hinata and go climbing once more—an adventure that will not only lead to new sights but also new friendships.