Kotoka, a first-year high school student, wants to play the trumpet, so she decides to join the brass band club, even though she has no experience! However, there was a long line of people who wanted to join the trumpet club, and everyone's eyes were on a third-year student, Mabumi. He is very talented, teaches carefully, and has a strong love for the trumpet. "His only(?) disadvantage is that he is too devilish! He is very close to me and I get nervous when he strokes me!" Can Kotoka do her best in club activities without succumbing to the charms of Mabun-senpai, who is strict with girls who are not serious? A serious, sweet, and touching coming-of-age love story!