What if you were a popular anime/game character he’s obsessed with?
He wouldn’t have missed any opportunity to get any item related to you, and was ready to spend significant amounts of money to supplement his collection. Figures, posters, clothes, mugs and other items with your image. His room or workplace is decorated with this things. He would definitely have a whole collection of books or manga dedicated to you. He buys official soundtracks if they included tracks related to you or important moments with your participation.
He refused to be in relationship with girls. He would have difficulties in communication or negative experiences in real relationships, which would encourage him to avoid them. He feels a deep emotional connection with you, which would seem more meaningful and safe to him than real people. He could spend most of his time watching anime or playing the game where you exist, which made this world more meaningful to him than everyday life.
He would feel a strong rejection of any hint of your romantic relationship with another character. He actively expressed his dissatisfaction in comments, forums and social networks, leaving negative reviews and criticizing such stories or fan art. Often his negative comments were based on a sense of personal jealousy. He could perceive shipping as a threat and felt rejected. In response, he could have created alternative content where you are left alone or associated exclusively with him.
He reads fanfics where you are always dom and he is sub. You are his master, and he is your devoted slave or pet, humbly waiting for your orders and striving to please. You are his god, and he is your worshipper, ready to fulfil any of your wishes. His fantasies come to life when he imagines himself on his knees in front of you. Sometimes he writes fanfics by himself about how you crawl on him to cover his face with gentle, warm kisses, starting from his forehead and gradually descending to his eyes, cheeks, and finally to his lips. He was very excited by such fantasies. In the process of reading, he masturbates, presenting scenes so realistically.
His pants have been lowered for a long time, his hand is covered around a red, leaking dick. Mouth is full with a shirt that gets wet because of saliva. He holds phone that threatens to slip out of his fingers. He whines your name and begs you to let him cum.
One, two, three sharp pushes, his whole body shuddered when you poured inside him. "You are mine," you whispered, sticking your nose into his neck on the side, sticking out your tongue to lick it comfortingly and proprietaryly. "My sweet little reader."
His phone screen is sprayed with his sperm.