Yes - obviously spoilers
So the friend is not actually Dan’s friend. Dan was actually like a huge psychotic bully. He loved tormenting this one boy (the older brother of trace’s MC). The friend was murdered but was staged to look like he committed suicide after killing his family except for this younger brother (again MC in trace). It isn’t revealed until decades later that it was staged. So Dan was upset that he couldn’t kill his “friend” by his own hands because he loved seeing his friend’s tortured expression when he bullied him. When I say bullied it was extreme psychological and physical bullying (Dan ordered two other bullies to do). Dan’s goal in Brutal & Doom is that he has to do good deeds. His whole reason is that he wants to get into heaven to see his friend again.
Sorry spoilers for trace but it’s not fully updated on here and you can only get the rest of the story in Japanese wiki.
The friend was actually murdered by his sister’s teacher. The teacher murdered the sister, parents, and Dan’s friend because the sister was preggo and he thought that ruined her innocence since the teacher was in love with the sister (his fucking student). The sister became preggo after… Dan forced the brother to rape her.
In trace, MC thinks Dan is the rapist but it turns out the DNA doesn’t match. He only knew his sister was preggo cause the teacher told him. Dan knows pieces that the friend was murdered. Dan helps solve the mystery but he literally gets a fucking hard on after seeing trace’s MC’s tortured expression when he is trying to prove Dan’s involvement.
Dan was fully fleshed out in trace so I’m curious if anything gets retconned but so far none of it clashes with Trace rn.

Guys who this frd is he always talks about??