Hi there, I've read a series wayback 2016 where the whole high school itself was transferred to different world and the MC awakened by killing the orc using the trap he set for the person who bullied him. When he came back from school a lot of students are dead and were rape by the orcs. It's a japanese web novel but have light novel too. It's a harem he has 4 female party(3 schoolmate and 1 elf native)
This is it! I stopped reading jp novels in 2018 so I already forgot the series that I've read. Thank you!