All of his overthinking and isolation comes from the fact that was deep down in his mind: "I am not loved nor will I be loved" that born from his parents' divorce, :feelsbadman:
You realize that this is a manga about her and her teacher understanding each other and get together right? And don't clump the goat Aoki with that shit of a human being, Aoki is always supportive not because of morbid senses but because he is genuinely nice and trying to help with the best he could