Sōjirō is the second eldest child of the Ayanokōji family. He is a muscular, heavily scarred man who can stop Kyōshirō's sword swings and endure Tarlotte's beatings. Whatever is said or done to Tarlotte by anyone, oftentimes it is Sōjirō who endures the wrath of her anger. Despite this fact, he seems to be the one most concerned with Tarlotte's well-being, even providing her with energy when she falls unconscious after a battle, despite the fact that Tarlotte attacks him when she finds him kissing her to provide energy without her permission. Sōjirō not only seems to feel compassion for the people who are temporarily drained of energy by Tarlotte, but expresses feelings of pity for all the Absolute Angels.

Unlike Kyōshirō's and Mika's behavior towards 'their' Absolute Angels, he seems to care for Tarlotte as a person, doing his best to keep her happy and worrying for her safety. In contrast with his siblings, Sōjirō appears to be a peaceful and thoughtful individual, who cares for the fate of bystanders of his own initiative. Sōjirō seems to be aware early on of the way events in his world are spiralling out of control and tries to decide the best way to redress this situation.

Sōjirō resembles the Orochi follower Girochi from Kannazuki no Miko.