While I was never punished for something like Shinsuke went through, I was physically and emotionally abused by my mother and her family, and made to hate myself. Being called "ugly", "disgusting" and other loving terms of endearment like that led to me feeling I wasn't good enough for anyone. It came to the point where despite wishing someone would care about me, and having a codependent personality disorder, I avoid relationships beyond friendship. It didn't help that the only time I had a boyfriend who lived in the same country as me(FTR, I'm woman, albeit an ugly one), my mother and her family would judge him, speak ill of him and sometimes abuse his trust. That led to me hiding any LDRs (they ended badly anyway) and just being uninterested in people.
Also, the feeling of being ugly and disgusting, due to always having had weight problems, led to me agreeing to undergo plastic surgery, which I regretted all my life, and as an act of rebellion against my mother, I let myself go weight-wise, making me uglier as a result. However, I feel much more comfortable that way, as I can simply not fit anyone's standards and be myself. All of this, plus therapy, made me realize that even without the trauma of the shit I went through, I was already uninterested in men or women, leading to me coming out as ace.