To read all these comments and opinions i can agree on what yall see are true from you're point of view. But from my view as a child in the same situation in some terms i can confirm two things, one- yes the way his back story plays out is ridiculous and feels horrible written or rush as you might say, two- all of his trauma and the way his character developed although may seem incredibly unrealistic but is in fact real.
The "real" you see might not be as harsh as this but life can be mess up in the most unexpected ways, his obsession of Hinata isn't simply boiled down to just "yandere" like one of you said but it is his love, the only love he has ever received in his life, his will to live is equal to his love for Hinata and it's only natural that a human would want to live. (His crimes for the sake of art is just a part of his character and helps carry out his image more!)
Therefore his obsession is a form of living (to simplify humans live as a society because we need connections, Sora's only connection in such a long time was Hinata making it a deeper form of love than you would normally see).
And for those who wish Sora would turn to be a full on twisted mind villain due to his love for art and desire to reach "a higher rank of expression", thus not being the "usual kind" of sympathetic villain you are being what you said he is- unrealistic!. Humans aren't born with hate or a natural will to kill to reach that wish of yours, its only causes like these, to be taken away from your love and life to reach this insanity and even then you're still a human with emotions being controlled by strong needs provoked from wrong ideas!
Sora is a kid desperate for love. The only reason this type of villain is common because they take part as humans, if it was something else then you will have your true pure evil villain.
I took my time to write this because it affected me deeply, i hope you can have second thoughts about Sora from this.