Hirasawa Yui, a young, carefree girl entering high school, has her imagination instantly captured when she sees a poster advertising the "Light Music Club." Being the carefree girl that she is, she quickly signs up; however, Yui has a problem, she is unable to play an instrument.

When Yui goes to the clubroom to explain, she's greeted by the other members: Ritsu, Mio, and Tsumugi. Although disheartened at Yui's lack of musical know-how, they still try to convince her to stay to prevent the club's disbandment. After playing Yui a short piece which re-ignites her imagination, they succeed in keeping their new member and guitarist.

Along with the tasks of school and homework, Yui begins to learn the guitar with the help of the other band members, experiencing many mishaps along the way. However, with the school festival drawing near and Yui getting stuck with her practice, will the Light Music Club be ready in time for their debut?

[Source: MyAnimeList]

The seven Blu-ray disc volumes of K-ON! have an extra short anime "Ura-ON!"

Houkago Tea Time performs live on New Year's Eve.

The student band "After School Tea Time" (lead guitarist Yui Hirasawa, bassist Mio Akiyama, drummer Ritsu Tanaika, and keyboardist Tsumugi Kotobuki) are ready to graduate and take their band to new heights. But before they can do that, they must recruit new members to ensure the survival of the light music club!

Between band practice, club recruitment, and studying, the girls stumble through daily teenager life: concerts, college applications, holidays, and vacations. Along with junior club member Azusa Nakano, the girls of K-On!! are ready to make their senior year of high school a great one!

[Source: MyAnimeList]

Extra short anime "Ura-On!!" included in the limited edition of the K-ON!! Blu-ray.

A special episode of K-ON!! released in the ninth volume of Blu-ray and DVD. The girls plan a trip abroad and go to the passport office to apply for passports.

[Source: MyAnimeList]

Graduation draws near for Yui, Ritsu, Mio and Tsumugi, the four 3rd-year students of the Light Music Club. They, together with Azusa, decide to go on a post-graduation trip. Their destination, decided by lot, is London!

[Source: official site, translated by Cranston; emended]