Rock n' Roll may never die, but the Sakuragoaka Girl's High School Light Music Club might not be here to stay unless would-be drummer Ritsu Tainaka can find three more members to replace the graduated seniors. Determined to see that the beat goes on, Ritsu can get a little help from her friend Mio Akiyama on bass, and together they might be able to convince choir-inclined Tsumugi Kotobuki to join on the keyboards. But even then, they'll still need a hero, preferably of the juke-box variety with stars in her eyes. Instead they find Yui Hirasawa, who's looking for a club to join and who's never held a guitar in her life. But when Yui does pick up a beat-up six-string, it feels good in her hands, and it doesn't take long to understand that maybe she's finally found a place where she belongs. Because you can't stop the music when four girls share a dream, even if it's something as crazy as someday playing at the famous Budokan. It's going to be a long and winding road, but if they find their passion and follow their muse, they could go anywhere in K-ON!

A middle school girl named Yume sees something fall from the sky, and meets a pale violet-colored kitten named Mew. It turns out that Mew has the power of "Yume Synchro" (Dream Synchro), the power to enter dreams. In the dream world, the girl and Mew collect Dream Stones.