Blackmail tag.

Mahiro, the senpai, and Kariya, her kouhai, are office workers just finishing another busy day at work; Kariya tries to invite Mahiro to have lunch together but she gets taken aback, flustered she says that is a bit personal outside work, Kariya immediately saves face and tries to explain he just wanted to congratulate themselves after a hard work done (he is obviously interested in her) and Mahiro excuses herself by saying they should have a gathering with more colleagues another time to eat out.

Mahiro doesn't dislike Kariya, even thinks he looks hot and is quite nice, but she is wary of her secret life being exposed by someone getting too close to her, she is an Urakajoshi (secret account girl), the adult anonymous cam girls of Japan, posting content online with varied themes, even getting fucked by randos.

Another day when Kariya and Mahiro are having lunch, it is all revealed he was secretly one of her top chat members and he found she is an Urakajoshi, Kariya gets shady and wonders what should he do with the fact he knows his senpai is leading such a life, then he of course claims he will keep quiet if Mahiro lay down with him.

Blackmail setting aside, the narrative is a like a woman's fantasy "oh he's so bad, but so hot" / "so mean, but so nice" type of deal, even admiring his strong muscles as he pins her down, so Mahiro doesn't really hate it deep down. The book ends with Kariya keeping his promise to never tell on Mahiro, but making sure their secret activities will continue, even teasing her about uploading their night out on her account.

Base +8

https://www.dmm.co.jp/dc/doujin/-/detail/=/cid=d_664582/

Base +25