A teenage girl born from the Hīragi family. She joins the Hyakuya Sect to oppose her family. He tells her to become a vampire. He refuses to turn her himself but helps her whilst also keeping his own objectives a secret.
A young seraph with high experimental potential. He acts as a leader toward the other orphans and is considered to be charming. He is half-Russian with blond hair and blue eyes. Saitō gives him money to buy ice cream. His mother was a member of the Hyakuya Sect and gravely injured him by throwing him out of a moving vehicle. His parents died during the subsequent car crash.
A young seraph who Saitō picks up after his mother attempts to burn him alive in their apartment and then lights herself on fire and commits suicide. His father was also abusive. Saitō takes him to the same orphanage as Mika a few minutes before the Apocalypse begins, and Yu fights him the whole way.
The heir to the Ichinose family and one who opposes the Hīragi. Saitō encounters him multiple times after a weak attempt to assassinate him, repeatedly offering an alliance persistently.
The First Progenitor was the one who turned Saito into a vampire. According to Saito, he disregarded almost everyone in the vampire race except for Ashera Tepes, because he was bored and wasn't interested in them anymore.
Saito turned Ferid into a vampire. He disregarded Ferid because he didn't act according to his expectations.
Crowley was turned into a vampire using Saito's blood. It is unknown if Saito is aware that Crowley is sired from him.
Saito meets her while she is imprisoned in Ferid's mansion. She recognizes him as the one who tagged behind the First Progenitor and he talks to her about how the First was only interested in her brother Ashera Tepes.
Urd meets Saito at Ferid's mansion while Krul was imprisoned. He addresses Saito as Rigr Stafford and cuts off his arm. Saito asks if Urd is bored following the laws established by the First Progenitor and tells Urd to leave Japan. Urd questions him and says Saito is no longer a vampire. Saito reveals he worked with humans before leaving.