CHILDREN, Deadman Wonderland, and Hideout are really good in my opinion!! All of these lack the //gay// aspect (lol) but I really enjoyed them!
The vibe of MADK is pretty hard to replicate. This one is probably the closest. Similar character dynamic with obsession vs love. I don't remember if there are demons in this one, but it is supernatural.
https://www.mangago.me/read-manga/gesshoku_kitan/
I love Heartless. It's a little more gritty. Where MADK has moments where you get a break from the gore and tension, Heartless is nonstop pain.
https://www.mangago.me/read-manga/heartless/
Some other horror bls I like (no demons unfortunately):
https://www.mangago.me/read-manga/hikaru_ga_shinda_natsu/
https://www.mangago.me/read-manga/sleeping_dead/
https://www.mangago.me/read-manga/host_in_down/
heartless and the summer hikaru dies are also lovely..!!! i almost forgot about them
Ok. So... I just finished reading MAD K and I absolutely loved the gore, the tension, the intimacy and of course THE GAY DEMONS. I don't need something exact, but I really liked the main aspects of gore, gays and demons. Preferably with good writing, of course!