PLSSS

Heartless
(And others by same author)

https://www.mangago.zone/read-manga/heartless/

https://www.mangago.zone/read-manga/pufferfish_and_dolphins/

https://www.mangago.zone/read-manga/period/
https://www.mangago.zone/read-manga/mushihime/
https://www.mangago.zone/read-manga/strangers_from_hell/
https://www.mangago.zone/read-manga/drcl_midnight_children/
Recommending this cause I love the artist.

Some of them are not "extremely" disturbing, maybe just creepy

수가 도망감 (Novel link: https://booktoki463.com/novel/7948499?stx=수가+도망감)