Prologue
Izaya Orihara knew about psychological projection.
In high school, he often recognized it in his classmates. Many of the bullies would call their victims "dumbass," when they were the real dumbasses. Many of the catty, "popular" girls would call others "ugly," when they were the true ugly ones. It's a defense mechanism. Not many humans want to be honest with themselves when it comes to their own shortcomings.
Izaya was a genius when it came to psychology. Without his knowledge of the mind and its workings, he'd never be able to manipulate his precious humans. He would use this knowledge to force them into taking part in his experiments. Most of the time, the experiments he conducted came to predictable conclusions. Sometimes, however, they did not. These were the experiments that interested him the most, and in some cases, these experiments consumed him.
His obsession with Celty's head and the afterlife is a good example of this. Oh, how badly he wanted to know what awaited him after death. The results of that experiment were a mystery to him. He sometimes considered the possibility that he may never solve the mystery of the afterlife. He truly hated this possibility. He truly hated not knowing.
Another good example is a man. A man with dyed hair, a bartender outfit, and an unstoppable temper. To Izaya, however, Shizuo Heiwajima was no man. He was a monster. His inhuman strength, unpredictability, and unwillingness to listen to reason were all reasons why Izaya hated him. Also, Shizuo was sometimes smart. Izaya thought that this intelligence had no place residing in such a monster. That was a pain. As much as Izaya found unpredictable conclusions interesting, when it came to Shizuo, they infuriated him.
Yes, his hatred of Shizuo Heiwajima was something Izaya knew existed. It was a certainty, much like the coldness of a winter or the heat of the summer.
Izaya also thought he knew why he hated him. However, he was wrong about that little detail.
Izaya Orihara knew about psychological projection.
However, he didn't recognize it in himself.