Two childhood friends walk into a dying music club and accidentally become the school's worst detectives. The mysteries aren't the point, they're the excuse for Haruta and Chika to keep finding reasons to be in the same room, to keep playing music together, to keep mattering to each other. Every case wraps up tidily enough, but what actually sticks is watching two people realize that saving the club means saving what they have. The show knows it's slight. It leans into that lightness anyway, and somehow that's exactly what makes it work.
Haruta and Chika reunite at their high school with a mission: revive the struggling Wind Instrument Club before it gets shut down. Chika has quit volleyball to take up the flute as part of a new, cuter image, but Haruta, her childhood friend and total opposite, sees right through it. The two practice hard while hunting for enough new members to enter musical competitions. Complicating things, both develop feelings for the band instructor, Shinjirou Kusakabe. Then strange incidents begin cropping up around the school, and the club members must work together to solve them. The result mixes school band music, light mystery and romance with a slice-of-life feel.
