Laichi was physically abused by his dad. And the abuse got much worse as he grew up. He had to please his dad every night. Even if he did, he still got beaten brutally.

He became friends with Pompo when he was 10.
Pompo was 12, and he was not outright bullied. but his schoolmates was avoiding him because he was weird. He laughed at wrong moments, kept misnaming people, touched people inappropriately and such...

As they were emotionally away from other people, they started to depend on each other.
Though Laichi found Pompo annyoing too, his affection towards Pompo grew stronger and stronger. He pictured Pompo in his mind while Dad raped him, coz Pompo was the only thing he could love in his life.