Set in a world where history has taken a slightly different course from the one we're familiar with, K follows the story of a young boy whose life is caught in a psychic war between seven kings. Ashinaka High School is known for its unique setting: the entire campus is built on an island. Yashiro Isana, aka Shiro, is having lunch with a cat on one of the school rooftops. After his lunch break, Shiro goes on an errand for his classmate Kukuri to prepare for their upcoming school festival, only to be chased by some intimidating-looking men.

Isano Yashiro (aka: Shiro-kun) is a student at the massive Ashinaka High School that takes up an island in the bay. He's a little spacey, does not stand out much, is fairly well liked, and tends a small white kitten named Neko (Cat in Japanese). Unknown to most people, this is an era of Kings: Seven people linked by an unknown process to an artefact called the Dresden Slate that confers incredible power they can share with a clan of followers. Each is represented by a rank, colour, and fundamental power of Nature.Strange things start to happen, shortly after the death of the Seventh Colourless King, when a video of Shiro surfaces showing him gunning down a Homura (Third Red King) clansman in cold blood and claiming to be the new Seventh Colourless King. Now, with no memory of the incident, he must deal with the pursuit of two Kings and their clans, a follower of the previous Colourless King, the Black Dog, who is trying to kill him as anevil king, and Neko who has turned into a naked cat-girl that can dance between the perceptions of others.

This is the first year of high school for the four girls, looking for that very special club.The healthy and energetic Tainaka Ritsu (club president, drums) decides to join the school's Light Music Club, only to find out that the club is about to be closed — due to the lack of members. Without much ado she drags along her childhood friend, the shy, mature, and sensitive Akiyama Mio (bass). That leaves only two more members, required to keep club from closing. Luckily the gentle, calm, warm, and cute Kotobuki Tsumugi(keyboard) stumbles into the club, only to be "convinced" by the pleading Ritsu to stay. The last member, the easily distracted klutz Hirasawa Yui, can only play castanets, even though the club needs someone on the guitar, but she is "bribed" — with cake — to stay anyway.Will Yui be able to learn to play the guitar — the special one she just bought and loves so much — before the four girls graduate?

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!

Graduation looms for the founding members of the Light Music Club. With only a few precious weeks of school left, the girls decide to make the most of it and plan a trip abroad. Hawaii, New York, Dubai—many destinations are suggested, but after a little help from the club's precious pet turtle, Ton-chan, London is chosen as the host of their next misadventure! Yui Hirasawa, Mio Akiyama, Tsumugi Kotobuki, Ritsu Tainaka, and Azusa Nakano will visit famous landmarks, perform live music for Londoners, and eat all sorts of delicious food, all while stumbling clumsily from place to place. But the fun won't last forever, as heartfelt songs and goodbyes will be made as their high school days together come to a close. One thing is for certain though: the undeniable friendships these girls have formed is something that will carry on long after the final scene rolls.

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!

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

It is almost the end of the year, and Houkago Tea Time has been invited to participate in a live house on New Year's Eve! The iconic band members are Yui Hirasawa, the carefree guitarist who is enthusiastic to play music; Mio Akiyama, the shy bassist who gets embarrassed easily; Tsumugi Kotobuki, the gentle and sweet keyboardist who finds joy in normal activities; Ritsu Tainaka, the extroverted drummer who likes to tease Mio; and Azusa Nakano, the rhythm guitarist who is one year younger than the rest but slightly more mature. Performing in the set gives the girls the rare opportunity to meet various people from different bands, including the one that invited them, Love Crysis. Will Houkago Tea Time be able to delight their audiences successfully?

It is the final year of high school for Hirasawa Yui (guitar), Tainaka Ritsu (drums), Akiyama Mio (bass), and Kotobuki Tsumugi (keyboard); the founding members of the Light Music Club. Together with their junior member Nakano Azusa (guitar), they spend their days after school in the music room enjoying tea and sweets, and practising music. Amidst band practice, preparations for the new student orientation performance, scouting for new members, and student responsibilities they still have time for After School Tea Time.

Ever since the School Island Incident, in which the four Kings were involved, the Silver Clansman, Kuroh Yatogami and Neko were on their search for their master Shiro. Unable to find any leads to Shiro, the two were in a gloomy mood until they ran into Homura members, Rikio Kamamoto and Anna Kushima, who were apparently being chased by someone...

Ever since the School Island Incident, in which the four Kings were involved, the Silver Clansman, Kuroh Yatogami and Neko were on their search for their master Shiro. Unable to find any leads to Shiro, the two were in a gloomy mood until they ran into Homura members, Rikio Kamamoto and Anna Kushima, who were apparently being chased by someone...

In modern Japan, where history has strangely overlapped with reality. There, seven "Kings" with great superpowers existed. Along with their clansman to whom they shared their own power with, the kings each formed clans. Order bound by blue, red flames that cause chaos, irregularities that shine in white, and reforms branched off into green. The Kings, each with their own abilities, now... With "jungle" once again jumping back into action, the fates of the various Kings are brought together.