Koi wo Kuwaraba Oni Made

The "Clan of the Sacrifice" is bound by fate, destined to be eaten by demons if caught before the age of 20. After the death of his grandmother, college student Itaru discovers for the first time that he is a descendant of this clan. Just before his 20th birthday, his true identity is revealed to Hayate, the leader of the demon clan. In a shocking turn of events, Hayate suddenly kisses Itaru, leaving him momentarily frozen. "It’s different from the old days," Hayate whispers, "now we don’t eat you; we take your spiritual power through sex." As Itaru grapples with this revelation and is subdued by Hayate’s demonic power, he finds himself having his sperm drawn out by Hayate...!?

(Source: Tokuma Shoten, translated)

Note: The chapter count includes an extra.