oyasumi punpun has gets somewhat scary with the art style
you probably have already but have you read junji ito's manga? that shit is terrifying to read
lol stories w art styles that r p scary:
https://www.mangago.me/read-manga/offal_island/
https://www.mangago.me/read-manga/litchi_hikari_club/
https://www.mangago.me/read-manga/paranoia_star/
https://www.mangago.me/read-manga/crime_and_punishment/
https://www.mangago.me/read-manga/shiro_ihon/
https://www.mangago.me/read-manga/kijin_gahou/
andddd u can just check my list and go to the horror portion :)
https://www.mangago.me/home/mangalist/1031841/
https://www.mangago.me/read-manga/shin_yami_no_koe_kaidan/
https://www.mangago.me/read-manga/gyo/
https://www.mangago.me/read-manga/pumpkin_night/
https://www.mangago.me/read-manga/juujika_no_rokunin/
https://www.mangago.me/read-manga/diner/
https://www.mangago.me/read-manga/gajuu_the_beast/
https://www.mangago.me/read-manga/kimi_ga_niku_ni_nattemo/
https://www.mangago.me/read-manga/suicide_girl/
https://www.mangago.me/read-manga/balemount/
https://www.mangago.me/read-manga/doku_mushi_the_ruins_hotel/
https://www.mangago.me/read-manga/redo/
https://www.mangago.me/read-manga/gofun_go_no_sekai/
https://www.mangago.me/read-manga/gedara/
https://www.mangago.me/read-manga/pygmalion/
https://www.mangago.me/read-manga/mahou_shoujo_site/
https://www.mangago.me/read-manga/kamisama_no_iutoori_fujimura_akeji/
prefferably manga style