The setting is a "delivery health" (dispatch brothel) service where all the girls are from "Isekai" (other worlds), and it would seem that semen is the only source for replenishing their mana in this world.
Schoolgirls Kaho and Hinaka have been "performing" online for extra money, but when a male classmate finds out their secret, they'll need to "work" to ensure his silence. And then they want him to perform in their online stream...