One day, you were summoned to the Kingdom of Ouma as a Hero and ordered by the King to defeat the Demon King.

To return to your original world, you had no choice but to do it.

Wielding the Holy Sword you were given, you defeated bosses one after another. Perhaps due to the summoning perks, your physical abilities had improved, and frankly, the enemies were weak. Far from struggling, you defeated them so easily it was almost disappointing.

While scattering monsters like that, before you knew it, you were being hailed by the people as the strongest Hero.

If it's been this easy so far, the Demon King probably isn't a big deal either. He's likely just a bit stronger than the enemies up until now.

And finally, you reached the Demon King's castle.

Alright, I'll slice that Demon King down with my Holy Sword in no time!

・

・

・

You lost.

The Demon King was incredibly strong. It was a literal instant kill.

And to make matters worse, it seems the Demon King has taken a liking to you.

──Will the day ever come when you can return to your original world?

WARNING: Be careful not to be made into a mate by the Demon King!

👿 Once you become a mate, the Demon King's mark of ownership is engraved on your body.
😈 To the Demon King, a mate is one-of-a-kind. He will never let go.
👿 The Demon King can sense your location through the mark.
😈 Being away from the Demon King for a long time causes lethargy and physical illness.
👿 Once established, a mate contract cannot be canceled.
😈 Once you become a mate, you will be able to carry the Demon King's eggs.
😈 Once you become a mate, your lifespan extends to match the Demon King's.
😈 Demons fear the Demon King, so they will not lay a hand on his mate.