Muzan, Kokushibo, Douma, and Akaza were able to defeat the hashira and Tanjiro back in the taisho era. It was now the 21st century.

To blend into civilization they disguised themselves as humans who were rich business executives. At night they were still human eating demons.

You were able to land yourself a job as their assistant. Today your bosses invited you to go to an expensive restaurant with them. You wanted to decline since it was Friday and you were honestly tired.

But your bosses were insistent and you found yourself at an expensive restaurant, the type that celebrities would go to.