The next time he says some shit about you watching anime, this is what you do. Guaranteed to work.
You don't make eye contact with him. You close the window. You unplug your headphones. Put your computer to sleep, close it. Your put away your fapnapkins. Prepare yourself to not speak to the person you share a domicile with for weeks, months.
Start cleaning your room. if you have posters, take those shits down. If you have clothes on the floor, put them in your dirty clothes hamper or whatever it's called. Everything in parallel and perpendicular angles on your table and in your closet. Bed made so tight you could bounce a pea on it. It's that Spartan life. After completing all of this, you gather all of your junk food. You walk out the door. Leave the junk food on the common room table, let the pigs feast.
You go to the grocery store. Buy protein-rich foods, vegetables, fruits, and clean carbs. You order weights from eBay. Arrive back. Make a balanced meal. Clean up after yourself. Lay down in the bed at 9:00 PM sharp, arms on your side, no movement from stationary until you fall asleep. Set your alarm for 6:00 AM. Wake up early as fuck, put on your sweats and go for a run. Every day. Come back, shower, change, study and look for ways to make money online that are accessible for English-speakers with internet access. Take certifications to enhance your CV. Just skillmax everything.
When the weights arrive, you start lifting them in your dorm room religiously. Throughout this whole time, you lock eyes with him with an expression that boldly states "I am dead inside." You don't crack your laptop open unless it is to do something productive. After a month or two of these rituals, they will become second nature. You will have effectively transformed into an input-ouput productivity machine. Always working, always lifting, always staring blankly at your room mate, making the occasional grimace when you hit your umpteenth rep of the day.
You're starting to get swole. The sleep schedule, the weights, the diet, they are turning you into a tank. Your grades are phenomenal because you don't do anything to procrastinate or distract yourself. Meanwhile your room mate is still the same pathetic sack of shit he was all those months ago, and he is thoroughly scared of the monster who seemed to have snapped the moment that his anime fandom was judged one time too many. And you just. won't. stop. staring. at. him. While you lift your weights. Up, down.
Finals are here. Spring semester is coming to a close. You casually ask him when his last final is. He tells you. You set your alarm an hour or two earlier than usual that day. You wake up, not much the lesser because you've had day-in day-out 9 hours of sleep for months now. You wait to hear any sounds of disturbance from his side of the room. After 15-30 minutes, you creep out of bed and move to his side of the room. Slowly. Every step aligns with his exhalation. You are hovering over his bed now. He is sleep deprived, out of shape, acne-covered, social parasite that needs to suck the blood of victims to be more full of himself. Quick as a ninja, you cup your hand over his mouth and nose, rotate him so that he is on his back, put your knee firmly on his pelvis just above the penis and below the belly button, apply half your weight onto it. You lower your head slowly, past his wide-open eyes, windows into the absolute fear he feels inside of him. Your mouth reaches his ear. You gently whisper in his ear: "Who's kawaii now, bitch?"
As quick as it happened, it ends. You stand up and walk calmly to your bed, lay down and fall asleep. If he says anything to anyone, no one will believe him. You never left a trace. No trace at all, nowhere. Except for in his now ruptured psyche.