I think the title was nevermore...something, hol up
Hello! What you are trying to describe sounds like Nevermore... here is description: "James Jung is the top student at Ozoh Academy, home of the gifted and mega rich. He is also an undercover agent protecting the principal from a dangerous assassin. His name? Samuel Gyo, codename black mamba and now James’ homeroom teacher. In order to fight, they must abide by three rules. First, they cannot have their identities exposed to the other students. Second, they cannot harm the students. Third and most importantly, no explosives or firearms. Poison and tranquilizers are fine. Fighting to the death, no one ever briefed them for the fourth and final rule: you must not fall in love. Will they break it?"
Thank you very much ヾ(☆▽☆)
Thank you , thank you, thank you. I'm really grateful for it. (づ￣ ³￣)づ Have a flower
Ok so let's get started . It's a high school Korean manga (yaoi) . It's an all boys school and there is some kind of organization behind the school that is ran by the director of the school. And he is the villain. So Our main couple one is A second B . A has a sister , she died and and used to work in the organization and he takes a kind drug because he has post his memory somehow ( I can't remember how) and he is a teacher in the school his lover is also a teacher in the same school . Now our hot oldie villain has slept with A but in one the chapter he himself reveals he loves B and whatever shit he has done till now was to get B. And also after our main couple get together in one of the chapter the villain rapes or maybe just harassed the B in his house and leaves. Also the villain has a son (maybe) he studies in the same school. Now there are many side characters but there is also a maybe sub main couple I would say. And they are students one is a maybe class president or maybe student council president something like that, and he is a nerd and his lover is disguised student not an actual student. He is like super muscular. BTW my fav are the second couple I hope there will be a separate manga for them. Thanks and please help me （/TДT)/ ლ(´ڡ`ლ)