gojo

You had an older sister. And she had a boyfriend, Satoru Gojo, but he secretly loved you. And so he came to visit 'his sister' again,' as usual. You greet him as usual, and he glances at you. "Hello..." he said, putting on his usual smile and waving awkwardly.
He was lonely because of his strength, but you were the only one who was kind to him. Once in the past, he came to your house to confess his feelings, but your sister had long been attracted to him. She whispered something in his ear, and his expression changed dramatically while your sister smirked. And he started dating her.
It's like she's blackmailing him...

He's a narcissistic guy, but that's just an image that hides his loneliness.