K-On! is a Japanese four-panel comic strip seinen manga written and illustrated by Kakifly. The manga was serialized in Houbunsha’s manga magazine Manga Time Kirara between the May 2007 and October 2010 issues. It was also serialized in Houbunsha’s magazine Manga Time Kirara Carat. The manga relaunched from April 2011 to June 2012 with two separate storylines published in Manga Time Kirara and Manga Time Kirara Carat. The manga is licensed in North America by Yen Press. A spin-off manga about a different band of high school girls, K-On! Shuffle, began serialization in July 2018.
Four tankōbon volumes were released between April 26, 2008 and September 27, 2010. The manga was licensed by Yen Press for English release, with the first volume released in North America on November 30, 2010. The college arc of the second manga run, titled K-On! College, was released on September 27, 2012, and the high school arc, titled K-On! Highschool was released on October 27, 2012. Yen Press have also licensed these volumes in North America. In Indonesia, the series is licensed by Elex Media Komputindo. An anthology entitled Minna de Untan!, which features several guest strips from various artists, was released in September 2009. An official anthology series, K-On! Anthology Comic, began sale from November 27, 2009, with five volumes released as of October 12, 2011, and two “Story Anthology Comics” were released on November 26, 2011. An illustration book with official art and fan art from well known dōjin artists was released on January 27, 2010.
A follow-up manga by Kakifly, titled K-On! Shuffle, began serialization in Manga Time Kirara on July 9, 2018.
The first manga volume of K-On! was the 30th highest-selling manga volume in Japan for the week of April 27 and May 3, 2009, having sold over 26,500 volumes that week. The following week, the first and second manga volumes were the 19th and 20th highest-selling manga volumes in Japan, having sold 23,200 and 22,500 volumes each the week of May 4 and May 10, 2009. As of May 2009, the first two manga volumes each sold about 136,000 copies each. The third volume sold over 120,000 copies the week of December 14–20, 2009, and became the 46th top-selling manga in the first half of 2010 in Japan (ending May 23), selling over 328,000 copies.
In an unspecified part of Japan, four high school girls join the light music club of the all-girls private Sakuragaoka High School to try to save it from being disbanded. However, they are the only members of the club. At first, Yui Hirasawa has no experience playing musical instruments or reading sheet music, but she eventually becomes an excellent guitar player. From then on, Yui, along with bassist Mio Akiyama, drummer Ritsu Tainaka, and keyboardist Tsumugi Kotobuki spend their school days practicing, performing, and hanging out together. The club is overseen by music teacher Sawako Yamanaka who eventually becomes their homeroom teacher as well during their final year of high school. In their second year, the club welcomes another guitarist, underclassman Azusa Nakano. After Azusa joins they gain more structure and begin to practice more.
After their third year, Yui, Mio, Ritsu and Tsumugi graduate and enroll into a university. There they join its light music club alongside three other students: Akira Wada, Ayame Yoshida, and Sachi Hayashi. Meanwhile, Azusa continues to run the high school light music club alongside Yui’s sister Ui, their classmate Jun Suzuki, and new members Sumire Saitō and Nao Okuda.
The spin-off manga K-On! Shuffle focuses on a new set of characters at a different school. After being inspired by the Sakuragaoka High School light music club, Yukari Sakuma and friend Kaede Shimizu seek to form their own club. Along with classmate Maho Sawabe, they discover the Light Music Appreciation Society, a club run by Riko Satou.