Silent Miyashita-san's Sexy Channel

Kei Sakai, a high school boy, had a problem. One thing led to another, and he was deeply uninterested in everything and had no sexual desire. Then one day, he learns of a mysterious, beautiful girl named Yami, who is the talk of the town on SNS, from a fellow part-timer. Yami is an unidentified internet idol who uploads naughty videos and pictures of herself in outrageous outfits, and has a huge following among men. No one knows her real face, but Sakai recognizes a woman who resembles Yami. That person was Saki Miyashita. Saki Miyashita is a high school girl who sits next to Yami in the same class, and although she is far more plain than Yami, she shares Yami's style and the position of the mole on her face. Sakai, who had lost interest and sexual desire, decides to explore Miyashita with an onlooker's spirit in order to find out Yami's true identity. However, unaware of Miyashita's trap, they end up sharing a absurdly lewd secret...!? (Source: Takeshobo, translated)