why does it all hurt so bad?!?

Eren is 15 he has never known love. His mother died giving birth to him. His dad has always blamed eren, his dad abuses him. Eren has always thought it was his fault. He also has to go through being bullied by assholes because the teachers don't give a shit. He has self harmed for 5 years no one cares. He had a best friend but that's gone now.
Levi is 17 he is one of the strongest boxers at wings high(their high school). He has had his share of tough times but nothing like eren. Levi is mysterious no one really knows a lot about him. what will eren find out?