Why is he doing all this again?? The top?

The ml's mom died and his world was shattered when his estranged dad took him in. His dad was giving him a new life his mother couldn't I'm assuming due to illness. When his life became normal again he saw the seme killed his dad then burned his house down with both of them still in it. The ml wants the seme to feel the pain he felt due to the semes actions. It's kinda weird how he's going about it but whatevs I'm here for it lol