Carnival from 8 Tatami Mats

The manga centers on Ryokuta Hanazawa, a high school boy who is so low-key that he remains unnoticed by most people even in class. Shio Mizuno, one of the smartest and most talented girls in school, sits next to him. One day, he spots Mizuno filming herself dancing in costume with a mask on in a lonely part of a local park. Ryokuta finds out that Mizuno uploads her dances to video sites under the pseudonym Smile, and he gets the idea to do his own anonymous dance videos to express himself, filming his dances from his own room. (Source: Anime News Network)