|Japanese Voice||Tomokazu Sugita|
|English Voice||Mike McFarland|
Shuji Isaki (伊佐木修) was the former Gon Sojo of the Ikai district from the Kōgon Sect.
In the OVA, Isaki's past is revealed, especially his hatred for his older brother. Isaki was made a contracted monk due to his brother's contacts. He intended to use Minai to kill his older brother, and then claim that his brother was unholy and became a Shikabane. Near the end of the OVA, it turns out that they had a bond because they had a met a long time ago as children. In Isaki's family store, which young Minai went to frequently. Isaki showed little compassion for Minai, but somehow, he actually did care for her.
In chapter 2 of the manga, Isaki, along with his unnamed shikabane hime suddenly got killed off while battling against Mizushima after Keisei and Makina recieved a report from one of the monk investigators from the city of Ikai. Later in chapter 16, as a result for his death, his rank would finally be claimed by Takamasa Sogi after the Kōgon Sect favored him through promotion.
In the anime adaptation, Isaki first appeared in episode 2 when he, Minai and Keisei were dispatched to investigate a number of murder cases involving 3 missing shikabane children who mysteriously escaped from their funerals. Isaki often did not care about others, especially his shikabane hime, Minai Ruo, who often gives her harsh treatment by forcibly ordering her for his own personal benefit regardless of her strong loyalty towards him. In episode 8, His bond would be broken after antagonizing a group of punks during a shikabane hunt, were they would seek vengeance, ambushing Shuji and stabbing him to death. Fortunately, Minai would still manage to survive for the time being, but was in a potential risk of reverting to a rogue Shikabane as her Contracted Monk was no longer alive. Later in the episode, she would be terminated when Ouri, fearing for her life after Saki tried and failed to destroy her, took her to the cafe where he worked, ignorant of the knowledge that his employers were also contracted monk & shikabane hime, Sadahiro and Akira. Akira quietly put her down (without Ouri being present) and both Minai and Shuji were given proper rites for dying in the line of duty.