Oshi ga Tonari de Jugyou ni Shuuchuu Dekinai!

Oshi ga Tonari de Jugyou ni Shuuchuu Dekinai! summary:

Manaka Sakiko is a huge fan of Chihiro, an idol from the idol group Haruiro Sunshine, and on her first day of high school she finds out the new girl sitting next to her is none other than Chihiro herself. No one else recognises Chihiro, so Sakiko resolves to keep her knowledge under wraps, but when she accidentally slips and reveals she's a fan, she unwittingly makes herself the enemy of another Chihiro devotee, one who isn't keen on sharing.