In general, 'k on' is not a strict adaptation of a true story. However, the way it portrays the daily lives of high school girls, their love for music, and their interactions within the club has some basis in real - life scenarios. For instance, the idea of forming a band and the challenges and joys that come with it are real experiences that some people have had. The anime just takes these common experiences and wraps them up in a fictional and entertaining story.
K19 is purely fictional. It doesn't have roots in real events. The story was crafted to provide an engaging and thrilling viewing experience, not to recount actual happenings.
K-On is purely fictional. It's the imagination of the creators and not rooted in any real-life events or people. The characters and their experiences are made up to tell an engaging and enjoyable story.
There isn't a 'k on' anime that is a pure, direct adaptation of a true story. But if you want to see anime with elements related to real - life high school and friendship like 'k on', you can check out 'Clannad'. It has a very real - life - like portrayal of high school life, relationships, and family.