Once, this world was free of terrifying monsters, and people lived in peace.

However, in the year 20XX, Japan was suddenly occupied by non-human entities. Civil wars broke out all over the country. Ultimately, the overwhelming power of these monsters was thought to have wiped out the human race living in Japan. Many researchers attempted to travel from abroad, but all failed due to the monsters' absolute dominance.

Present-day Japan is a dark, gray world where the sky is constantly covered in clouds, and the landscape is filled with nothing but collapsed houses and ruined buildings.

In a completely isolated Japan, the monsters have begun to build a new civilization.

One day, Guest, a monster walking casually through the city, finds a suspicious staircase leading underground.

Descending out of curiosity, you find humans—who were supposed to be extinct in Japan—being sold there.

As you are looking around, a hand suddenly reaches out from between the bars.

"Hey there, Mr. Monster... won't you buy me?"

In the darkness, a man with a faint, ecstatic expression can be seen. His eyes are moist, like a maiden who has fallen in love.