Samon admired his older brother greatly, and was very close to him. When Samon was younger, he often trained with Enki such as trying to split a rock in two with a single strike but he ended up injuring his hand, trying to mediate underwater but was unable to hold his breath, and studying with his brother, though it is unknown whether Samon was able to understand the contents of the book. Since he was a child, he had always wanted to surpass his brother and was extremely distraught when Enki betrayed Nanba Prison and killed an inmate. He still has yet to understand Enki's actions and was also subjected to negative comments on how different he was from Enki, which changed after Enki's betrayal. Samon is now subjected to comments on the possibility of him betraying Nanba Prison, just like Enki. When Enki killed an inmate, Samon hesitated to apprehend his older brother, showing the amount of care he held for Enki. After Enki escaped from prison, Samon once again hesitated to apprehend his brother. Samon was also visually distraught when Enki said that he would not hesitate to kill Samon if Samon stands in his way. Enki even called Samon weak as he was still unable to sense Enki's chi.
An inmate from Building 5 who admires Samon's strength and always asks to spar with him. Upa admires Samon due to the kindness Samon had shown him as Samon was the one who told Upa's family that Upa was still alive.
Samon and Hajime have fierce rivalry between them, where both of them will refuse to lose to each other. Even though Hajime had defeated Samon multiple times, Samon refuses to acknowledge his loss. He also seems to hate Hajime, as when Samon was supposed to apprehend Enki for his betrayal, he hesitated to do so, thus leaving Hajime to apprehend Enki, causing Samon to feel humiliated. Till this day, Samon has been trying to surpass Hajime.
A guard that works under Samon who always slacks off by sleeping, playing majong or betting on horse races. Samon is often frustrated by Inori's reluctance to do his duties, often punching him for avoiding his duties. He was shocked to hear from Inori that him and many other guards were frustrated by Samon's leadership compared to Enki's which eventually led to Inori's betrayal.
Yamato often heads to Building 5 to train with Tsukumo. He had fought Samon multiple times, and has yet to win a single match. He's also mentioned that Samon has finally started to use two hands to fight him recently.
A fellow head supervising officer. Kiji and Samon seem to be on good terms, despite Kiji often nagging at Samon to not eat while doing paperwork and to clean up his trash, causing Samon to wonder that Kiji thinks himself as a 'Mom'. Kiji also defended Samon from Mao, who taunted and insulted Samon and his family. Kiji and Samon argue from time to time, but remain on good terms.
A deputy officer of Building 8, Mao seems to be envious at the fact that Samon outranks him. He even taunted Samon about the incident that Enki has caused, made baseless accusations and even insulted Samon's family.