I’m looking for any manga (excluding yuri/hentai and most yaoi) containing psychological and dark themes that you recommend

Your neighborhood sad girl

Try reading zekkyou gakkyuu, and the promise neverland

"Bravery we all have it"

Hyouryuu Kyoushitsu is considered a classic of horror manga, I enjoyed that. SANBE Kei is a really great author who has done several horror/survival manga that were very good. I also strongly recommend the oneshot Zanuff the Butcher, which is extremely dark, but is probably the best oneshot I've ever read.

“Oyasumi pun pun” is a manga that deals with several mental disorders (which are pretty accurately represented, give or take certain details) ranging from clinical depression and phobias to bpd and schizophrenia. It’s very realistic so can become extremely depressing and bleak (maybe even boring) and other times disturbing, but is a very good read. Discusses domestic violence, depression, dissociation, trauma, anxiety, attachment issues, trust issues, rape committed by someone you trust, self blame and suicide.

“Nii Chan” is a really dark and disturbing read which focuses on the effects pedophilia has on a victim in their life when they get older and the reasoning behind the actions they do. It also addresses abusive relationships and homophobic abuse, victim blaming, rape, and drug use. Not for anyone under 18 or anyone who’s sensitive to things of this nature. It’s really depressing and leaves a bad taste in the mouth.

“Kami no Kodomo” (anything by this author is disturbing) illustrates with an abstract art style psychopathy from the perspective of the psychopath. It deals with mutilation, cannabilism, pedophilia, and rape (isn’t an edgy representation, actually creepy).

“Monster” is a very good, classic psychological thriller which deals with moral judgement, psychopathy, secondary trauma, suicide, identity and dissociative amnesia. It’s literally so amazing (though slow) it’s totally worth it. A manga and an anime, both are the same but you can watch and read both if you want.