Naimononedari no Kimi ni Hikari no Hanataba wo

Kageko is a high school girl who has a complex about being "ordinary" in every way. However, during the second semester, she ends up sitting next to Mahiru, a popular student at school and a member of a hugely popular idol group. She thought she lived in a different world from him, a "special" boy who is the complete opposite of her... But by chance, they end up serving as library committee members together! What's more, it seems he has a side to him that those around him don't know about...?

Source: Comic Walker, translated