Comment by Batou on Askel

@Askel @Akhi Sultana 
Some of these belong in isekai genre,, all of them I consider dark fantasy.

https://mangabuddy.com/the-wolf-wont-sleep
https://mangabuddy.com/tensei-shitara-dragon-no-tamago-datta-saikyou-igai-mezasa-nee
https://mangabuddy.com/worthless-regression
https://mangabuddy.com/mookhyang-dark-lady
https://mangabuddy.com/nigoru-hitomi-de-nani-wo-negau-highserk-senki  ****** (I compare this to Berserk)
https://mangabuddy.com/saihate-no-paladin
https://mangabuddy.com/king-of-the-labyrinth
https://mangabuddy.com/tower-dungeon
https://mangabuddy.com/yajin-tensei-karate-survivor-in-another-world
https://mangabuddy.com/blinded-by-the-setting-sun
https://mangabuddy.com/reincarnation-of-the-suicidal-battle-g**
https://mangabuddy.com/goblin-slayer

Hope you have fun with this.