闇バイト先は異世界でした, My dark part-time job was in another world.

Ryuji Hashiba, a high school student, has to give up on his dreams and work to earn money for hospital expenses after his parents fall ill. One day, Ryuji finds a part-time job that is incredibly expensive, and even though he knows it's questionable, he joins to pursue his dream once again. After passing through a mysterious door as instructed by his employer, an unknown world opens up, and suddenly monsters attack...! ?