Boku no Pico..
wait that's an anime FUCK nvmnvmvnvmnvm.
has a manga too
The best manga http://www.mangago.zone/read-manga/berserk/
i love that manga too but im already reading it may be something similar :)
http://www.mangago.zone/read-manga/gantz/ (I did not get too far, but it was disturbing)
If you want good horror manga i recommend you to read everything by Ito Junji the master of horror and you can also try horror manhwas with sound ヾ(❀╹◡╹)ﾉ~
I also didn't get too far, because it was boring... Psyren (similar story, but for a younger audience) was better
can anyone recommend a good horror manga