Najenda: His master who woke him from his slumber. He follows her orders without question. When asked by Leone and Tatsumi why he chose Boss as his master, he stated that she resembled his old master from many ages ago. Unfortunately this master was a man, which greatly upsets Boss. Susanoo's abilities always greatly impressed Najenda which pleased Susanoo for being able to be of service to her. When ensuring Night raid's escape from Esdeath after the assassination of Borrick, Susanoo felt at ease knowing that the distance between him and Najenda would mean that her life would no longer be in danger after she used his trump card.
Lubbock: Shared a one-sided rivalry where Lubbock continually tries to outdo Susanoo in the hopes of impressing Najenda. However, this soon subsided when Susanoo mentioned to Lubbock that as a Teigu, he had no such feelings when it came to romance. Lubbock then promised that he and Tatsumi would help Susanoo out with this by helping him find a woman he liked. The two also shared a mutual bond of comradeship when both stated they would never forgive Borrick for his abusing of women and his degrading of food.
Chelsea: They were both new to Night Raid and are both stuck in the middle as time passes. It took a while for them to get along with Tatsumi and the other members of Night Raid.
Akame: The two of them shared the same interest in food as seen in one part of a chapter when the two of them went fishing.
Leone: In the preperation to the assasination of Borrick, both leone and Susanoo dug the tunnell to lead to the mansion. Both greatly enjoyed themselves while doing so.
Tatsumi: Susanoo helped train Tatsumi and gave him advice in order for Tatsumi to preserve his strength. Tatsumi extended his hand in friendship, saying he thought of Susanoo more as a comrade than a Teigu and asked for Susanoo's help in helping him and Lubbock in getting girls. They solidified their friendship with a fist bump. Upon Susanoo ensuring the remainder of Night Raids escape after the assassinaton of Borick, Susanoo displayed his fist to Tatsumi, to display their bond of friendship. As he charged into what he knew would be his death, Susanoo smiled that he met several good people, thinking about Night Raid, and had no regrets as he charged.