With World War II right around the corner, intelligence on other countries' social and economic situation has become a valuable asset. As a result, Japan has established a new spy organization known as the D Agency to obtain this weapon. Under the command of Lieutenant Colonel Yuuki, eight agents have been assigned to infiltrate and observe some of the most powerful countries, reporting on any developments associated with the war. In order to carry out these dangerous tasks, these men have trained their bodies to survive in extreme conditions and studied numerous fields such as communications and languages. However, their greatest strength lies in their ability to manipulate people in order to obtain the information necessary to give their nation the upper hand.

After meeting a dancing old man in what she thinks is just a crazy dream, a preteen schoolgirl embarks on a series of fanservice-filled magical girl adventures with a little creature named Ongo who might be evil and a shy girl with mysterious powers named Nami. (Source: ANN)

It is the new year, which means that the senior members of the Light Music Club are now third-years, with Azusa Nakano being the only second-year. The seniors soon realize that Azusa will be the only member left once they graduate and decide to recruit new members. Despite trying many methods of attracting underclassmen—handing out fliers, bringing people into the clubroom, and performing at the welcoming ceremony—there are no signs of anyone that plans to join. While heading to the clubroom, Azusa overhears Yui Hirasawa say that the club is fine with only five people and that they can do many fun things together. Changing her mind, she decides that they do not need to recruit any members for the time being. K-On!! revolves around the members of the Light Music Club as they experience their daily high school life. From rehearsing for concerts to just messing around, they are ready to make their last year together an exciting one!

A fresh high school year always means much to come, and one of those things is joining a club. Being in a dilemma about which club to join, Yui Hirasawa stumbles upon and applies for the Light Music Club, which she misinterprets to be about playing simple instruments, such as castanets. Unable to play an instrument, she decides to visit to apologize and quit. Meanwhile, the Light Music Club faces disbandment due to a lack of members. This causes the club members to offer anything, from food to slacking off during club time, in order to convince Yui to join. Despite their efforts, Yui insists on leaving due to her lack of musical experience. As a last resort, they play a piece for Yui, which sparks her fiery passion and finally convinces her to join the club. From then onward, it is just plain messing around with bits and pieces of practice. The members of the Light Music Club are ready to make their time together a delightful one!