In a world where people with more erotic stamina are considered strongest, with Ruka's endless stamina, he is the strongest in the world and even stronger in battles between the sheets! As a Knight under the great Fuckboy, he is sent to do the dirty jobs. When a magical beast attacks the Elf Mia, he steps in to protect her, dying in his heroic feat--or so he thought! Making up in a warm ecstasy, Ruka finds himself deep within this Elf's embrace. As confusion mounts, a voice echoes in his head, "Have you awoken? The person with endurance beyond that of a normal human will be the Zeshirin of the world!" Here begins an erotic fantasy with an ecstasy level of over 2000%!