Paychos

Not really a manga but
http://www.mangago.me/read-manga/stalker_x_stalker/

Head Over Heels manga

I am not sure but here’s some of my favorites where their “psychos”;

http://www.mangago.me/read-manga/osananajimi_irony/

This one seems normal but it gets even more Fucked up as it go’s;
http://www.mangago.me/read-manga/public_sex/

http://www.mangago.me/read-manga/you_re_my_favorite_toy/

This one really recommend not sure if it’s on Mangago, I think it fits you description perfectly;
https://zinmanga.com/manga/psycho/

Um I have a one shot book like that. You may not like it cuz it’s way too fucked up and it’s also 2 brothers

http://www.mangago.me/read-manga/ibitsu_no_kakera/

Um I hope you like it ╥﹏╥