So MC was NOT a minor, that explains his fear of having been recognized in the restaurant.
He looked like a highschooler in the first chapter...I'll give it a second glance, is possible the author did write his age, or possibly added years so to make sense how he can drive, got a real punishment and had his face on the news after a negative backlash from readers.
Even the law decided to be lenient, I wonder if his mother was really bullied by the neighbors or it was all in his mind.
Seems even clear that the mental hallucination he have of his sister changes based on his feelings, he wants to live, he wants to return to a normal life or the "phantom" wouldn't have supported him.
Sadly the author made clear how the girl bully doesn't want to stop, she will make research on him and find some way to ruin his life, she wasn't scared when running away.
And now I wonder if the girl wants him to recover as way to apologize for her father actions or wants to get close to him and give him a lot of despair, maybe kill his mother before his eyes, as the problem with her relatives was probably that they hated having the daughter of a rapist under their roof.