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?