https://www.mangago.me/read-manga/gunjou/
https://www.mangago.me/read-manga/hone_no_nazuki_made_aisu/
https://www.mangago.me/read-manga/seasons_in_bloom/
https://www.mangago.me/read-manga/the_chain_of_youth/
https://www.mangago.me/read-manga/your_fetters/
https://www.mangago.me/read-manga/savior/
https://www.mangago.me/read-manga/my_brother_and_i_are_rivals/
https://www.mangago.me/read-manga/on_a_leash/ (SPIN-OFF: https://www.mangago.me/read-manga/let_loose/)
https://www.mangago.me/read-manga/black_white_sal_jiang/ (it's been a while since I've read this but I think the two leads beat each other up a bit so avoid it if you're uncomfortable with that)
https://www.mangago.me/read-manga/officer_you_can_no_longer_hide_your_tail/
https://www.mangago.me/read-manga/indulging_a_crazy_beauty/
https://www.mangago.me/read-manga/i_love_amy/
https://www.mangago.me/read-manga/the_barefoot_nina/
https://www.mangago.me/read-manga/kill_me_now/
https://www.mangago.me/read-manga/ubai_ai/
https://www.mangago.me/read-manga/our_similarities/
https://www.mangago.me/read-manga/serenade_keum_kyesoo/ (toxic relationship between FL and prominent side character; age gap, teacher-student relationship but both characters are 18+)
https://www.mangago.me/read-manga/i_m_more_dangerous_than_you/ (age gap, teacher-student relationship but both characters are 18+, bullying, violence, kidnapping, confinement)
https://www.mangago.me/read-manga/manipulate_my_heart/ (age gap, teacher-student relationship but both characters are 18+, homophobia, abusive parents, human experimentation)
https://www.mangago.me/read-manga/chirizokonai_no_hiraeth/ (suicide and suicidal ideation)
https://www.mangago.me/read-manga/naraku_no_hanazono/ (incest and child sexual abuse [not between MC and FL], abortion, mild violence)
https://www.mangago.me/read-manga/love_thy_neighbor_2/ (age gap, adultery, religious themes, attempted kidnapping/human trafficking)
https://www.mangago.me/read-manga/outro/ (adultery, abusive parent)
https://www.mangago.me/read-manga/yodaka_meguru/ (adultery)
https://www.mangago.me/read-manga/my_girlfriend_s_not_here_today/ (adultery)
https://www.mangago.me/read-manga/efude_to_kurokinu/ (one-shot; adultery)
This is peak too but it's only a one-shot:
https://www.mangago.me/read-manga/adabana_no_yakusoku/
I’m in desperate need for some toxic yuri similar to “Destroy it all and love me in hell” but not to the point of “I love your cruddy” because I hate throw up and just the nasty stuffy they did I really didn’t like.