If you’re looking for awesome friendship in prison setting, « Rainbow Nisha », thought hard, is absolutely incredible and touching. (Generally a must read if you’re not too sensitive/easily triggered, it has a kind of realistic aspect.)
I also recommend you to check out « Eden no Ori », if you’re looking for an adventure with horror settings and friendship. It’s… an amazing journey I would say, with a really cool bestiary of « monsters » and marking characters.
Else, « shokuryou Jinrui » and its sequel by the same creators as AnT has really similar vibes, with the same kind of humor and interesting characters and monsters. To my taste AnT is still their best work, but SJ stays a satisfying read.
Can someone rec me a manga/manhwa similar to this?