Gari Tsutomu-kun to Uraaka-san: Sanzan Osewa ni Natteiru Ero-kei Uraaka Joshi no Shoutai ga Kurasu no Idol Datta Ken

A hardworking high school boy, Tsutomu Kariya's secret hobby is to scour social networking sites for erotic photos of girls. He is especially fond of a girl named “RIKA,” a JK with big tits, who he worships like a goddess.
One day, Tsutomu accidentally saves Mariya Rikka, the most beautiful girl in his class, from an incident. In the process, he finds out the “secret” that Marika has been hiding from everyone. Then, for some reason, Marika suddenly approaches Tsutomu and reveals herself to him in a way that he couldn't have expected...?
A secret-sharing romantic comedy that about the naughty "secret account" of the class idol!
(Source: Kadokawa, translated)