Adekan - this fits your description the best (think of the manga plotline of kuroshitsuji/black butler)
Mouryou Shoujo
Kurosagi Shitai Takuhaibin (Kurosagi corpse delivery service)- i LOVE this one. has elements of historical fantasy, as wel
Aftergod (it isnt rlly historical or fantasy, tbh, it’s more like chainsawman and modern, but the monsters are insane)
Oyasumi Jack the Ripper
Graineliers - most fantasy like. not rlly horror
Carp with Thousand Eyes- any horror is more along the lines of existentialism/morality
You will hear the voice of the dead (it’s like. episodic mystery. idk it reminds me of Goosebumps lol)
Survive Romance- probably the least fitting your description, but no joke when i say it has an insanely meta, chilling feeling
Yagiza no Yuujin - also not fitting ur setting, but it’s kinda eerie
^^ similarly, “The Planet Walks Alone”
annarasumanara (i recommend this bc of the artistic choices, it’s crazy good. feels fantastical. This might be more aligned in terms of atmosphere for what u might like, but not in terms of setting)
neko to okami
oyasumi punpun
Promised Orchid (more action, tho)
you mught enjoy “Dam of the Forest” and “Even the Demon King, One Step At a Time,” but the horror is isolated to bouts of existentialism, and therefore not entirely what ure looking for, tbh
Ghost Theater
I Love Amy (it’s like. rlly not fantasy or horror and it’s set in modern day, but it feels horror(?))
this gotta be the latest reply to your comment, BUT THANK YOU SO SO MUCH YOU'RE A LIFESAVER MWAH
hey guys is there any fantasy-horror mangas/webtoons you'd recommend? it'd be awesome if it was set if it was somewhat historical or placed somewhere like in a fairytale.