Natsuka Sakurai is one of the students from Class 3-2 during the second season of the anime. Natsuka is smart, sensible and helps others a lot. She is a good friend of Fūko Takahashi and is called "Nacchan" by others.

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!
 
(Source: MAL Rewrite)

With graduation right around the corner, every member of the Light Music Club except for Azusa will be leaving for good. But the girls aren’t going to let something as silly as graduation tear them apart! For their final hurrah, the girls are going on the ultimate vacation tour— all the way to London! Their overseas journey will lead them on a trip of discovery and friendship as they take the stage one last time for their final encore together. 
(Source: Sentai Filmworks)