Hajime Shishizaki

Hajime Shishizaki is a character that has, so far, never made a physical appearance in the series.

Characteristics
Almost nothing is known about Shishizaki in terms of his personality or his overall appearance. In terms of physical abilities, Shishizaki is said to rival both Izaya and Shizuo in agility and strength respectively. He was also apparently well trained as there are rumors saying that Shishizaki had beaten a US Soldier who was vactioning in Japan in a fist fight.

Background
What little is known about his history before the series is that he is the son of a rich family and that he attended Raira Academy with Shizuo, Shinra, and Izaya. He was popular at school and was a relatively good student. It is said that he would frequently get caught in the battles Shizuo and Izaya had although it is unclear if his involvement was intentional or accidental. After he graduated, he apparently worked at Russia sushi for a short while before either quitting or getting fired. Afterwards, Shishizaki eventually left Japan to study abroad in America.

Dragon Zombie Arc
Shishizaki is mentioned in passing by Shizuo. He remarks that he was one of the few people who could keep up with Izaya's raw agility.

Durarara Side Stories
Bits and pieces of Shishizaki's life are revealed in most of the durarara side stories that were published in various magazines.

Shizuo Heiwajima
Main Article: Shizuo Heiwajima

Shizuo refers to Shishizaki as his sempai and seems to hold some degree of respect for him. Other than that, little is known about the two of them

Izaya Orihara
Main Article: Izaya Orihara

Izaya appears to have a negative impression of Shishizaki as he gets visibly annoyed when he is mentioned. When rumors start to circulate about Shihizaki's return from overseas, Izaya appears to be visibly disturbed.

Trivia

 * Since the durarara sidestories are the only consistent source of info on Shishizaki, fans have started referring to them as the "Shishizaki monthly."
 * Volume 09 is the only time in the main series to have any reference to Shishizaki's existence.