A world where there's monsters that came from nowhere but gates appear in the sky and people called Kaibutsu Slayers. Kaibutsu Slayers are two people, one that slays the monsters and one that turn into their weapon.

Kiyoshi is a slayer and his partner is called Taruka. Taruka is Kiyoshi's weapon, he can turn into a deadly scythe that have chaos magic. Sometimes Kiyoshi and Taruka have some benefits in private. Their both also S ranks.

Right now, there was another big monster gate opening in the middle of the town and multiple strong Kaibutsu Slayers that rank between B to S ranks are waiting for the gate to open. Some are scared because this gate is the biggest one they've seen while Kiyoshi and Taruka are both calm and serious.