Karen, my girlfriend's sister, is very attached to me. At first, I even found her annoying... But my feelings changed when I started to suspect that the man she was going on a trip with was a man. I used your sister to distract myself from my anxiety about her... If she's going to cheat on me, I'll cheat on her first... That's how I felt, but... My actions towards Karen, who accepts anything, escalated. Cheating, betrayal, and sex were not enough for me, so I blindfolded her, handcuffed her, trained her, and...