Yami Baito Saki wa Isekai Deshita

Yami Baito Saki wa Isekai Deshita summary:

If you don't earn money, you can't survive!
When his parent falls ill, high school student Hashiba Ryuuji has to give up his dreams and start working to earn money for his mother's hospital bills. One day, Ryuuji finds a part-time job that pays an unbelievable amount, and even though he knows it's suspicious, he joins to pursue his dream once again. Following his employer's instructions, he passes through a mysterious door and finds himself in an unknown world where he is suddenly attacked by monsters...!?