The day after seeing the ending of the game 'Regressor D-Class Hunter,' Yeon Sunwoo, who has become an extra in the game, is kidnapped by the protagonist, Lee Jaehee. Lee Jaehee, suffering from insomnia, proposes a contract, saying he needs the mentalist Yeon Sunwoo, and they enter into a contract. Albeit, somewhat forcibly. [Listen to your master and become a beloved servant!] "...A beloved servant? Master? What is this nonsense?!" Isn't this a 'slave contract'?!" To return to the real world, he must find the hidden ending. Will Yeon Sunwoo be able to escape the game?