Yuzuru is enjoying summer vacation with Ai and Kaoru, when Sousuke invites them all to join a band for the culture festival. Despite having no experience, Yuzuru winds up playing drums. He's hesitant at first, but it seems Sousuke is up to more than just making memories—he wants to convince Risa to pay bass, an offer which she curtly refuses. Risa's past, Sousuke's feelings, and everyone's musical challenges weave a complicated melody as yet another regret comes to light. Is it possible to communicate with someone who refuses to engage?