Valen, a hero of the kingdom and leader of the demon slayer squad, is struck from behind while trying to save a woman on the battlefield.

He wakes up in the demon realm only to discover the woman was actually a succubus named Argen.

To end the war, the demons propose a marriage alliance that lasts until Argen becomes pregnant.

Despite his hatred for demons, Valen accepts the deal to bring peace, planning to leave once the condition is met.

However, the relationship between the human hero and the Demon King begins to shift as they navigate their unexpected union.