After Luke’s boring life ended because of an unexpected accident, he reincarnated and became a labyrinth explorer. However, he couldn’t advance beyond E-rank, despite being an explorer for 15 years. Furthermore, the guild has a rule that mandates explorers to retire if they do not reach D-rank by the age of 30. Since there was only a month left until Luke turned 30, impatience drove him to accidentally trigger a warp trap he wouldn’t normally trigger. In the unfamiliar room he found himself in, he came face-to-face with a woman of peerless beauty. Then, shocking words came out of the woman’s mouth, “My brethren…A vampire won’t get stronger by slaying monsters. We only gain strength by feeding on blood.” In order to become stronger, to rise above D-rank, and to get blood, Luke becomes the ruler of the night and begins feasting on the women of the labyrinth city.