The story is set in a near-future society devastated by a global pandemic. Unlike typical apocalyptic scenarios, this virus has a specific and peculiar effect: it has rendered almost every male on Earth impotent. The protagonist, a high school student named (sometimes referred to as Kazuki), is the rare exception to this rule—the only "Adam" in a world of "four billion Eves" who remains physically capable.

And then, softly: "The Modaete Protocol is a cage, Kenji-san. You wanted a god’s control. But what you really want is something much harder: a peer."

An upbeat and friendly senior who is the first to discover Itsuki's secret and claims exclusive "rights" to him.