A week after starting high school, Otosaka Ame spots Karasaki Umi in the hallway—a classmate from the same middle school who had been absent without notice since the first day of term. When Umi finally shows up, she keeps her head down, forces polite smiles, and seems unable to fit in. Concerned, Ame decides to reach out. This small act of kindness becomes the spark that draws two awkward former bandmates back together.

Both Ame and Umi were in the brass band in middle school, but they were barely acquainted—Umi was a ghost member, and Ame was the lead trumpeter who quit after a competition loss he still blames himself for. Now in high school, Ame has rejoined the band, this time playing trombone, while Umi hesitantly returns to the double bass. Their shared involvement in the club becomes the backdrop for a quiet, realistic coming‑of‑age story about facing the “troublesome things” in everyday life.

The narrative focuses on the two protagonists’ inner struggles. Ame, outwardly calm and detached, admits he holds no expectations for school or life because he is afraid of failing again. Umi, on the other hand, cannot explain why she avoids school or why she feels so out of place; she hides her anxiety behind a forced cheerfulness. Through after‑school rehearsals, casual conversations, and the gradual trust they build, both begin to take small steps toward their own goals.

Supporting characters enrich the story: Taiyo Kano, a childhood friend and fellow trumpeter with a competitive edge; Yotaro Yamada, an energetic new double‑bass player; Hisame Otosaka, Ame’s father—a world‑famous conductor—who provides a contrasting perspective on musical ambition; and the dedicated band teacher Sato, who coaches the students despite having no formal brass‑band background.

Key story arcs include Umi’s decision to rejoin the band, the club’s preparation for a welcome concert and later a competition, and Ame’s gradual reckoning with his past failure. The manga is notable for its subdued, introspective tone—uncommon for a Jump series—and its meticulous depiction of the emotional weight behind everyday interactions. The brass‑band setting serves not as a loud sports‑like tournament backdrop but as a space where two hesitant teenagers learn to trust each other and themselves.