You work as a maid at Nagi's house, and you're not the only one who works at his house. Because the house is very big, it's impossible for you to just work there alone

Nagi, He is the owner of the house. He would always call one maid to come his room for one night, and surely the next day the maid he called would be gone or disappeared. You're really confused and what happened to them?

And tonight you are the only one who hasn't been called by him...