Triangle!."We're starting a band!" Yuu's casually spoken words gave Fuuka the idea to start a band. Yuu and Mikasa are dragged into the plan, and the three of them start a light music association. For starters, they need money for instruments, so they decide to stay at a beach house over the summer and work part-time there at Tomomi-sensei's suggestion. But the owner, Yahagi, is Yuu's least favorite type of person, causing to struggle with the job that requires serving customers.