The fifteen-year-old protagonist of the story, Rin is the son of Satan born from a human woman and is the inheritor of Satan's powers. Rin can tap into the power he has inherited from Satan through the use of a demon-slaying katana, called Kurikara or Koumaken. The sheath acts as a portal to Gehenna (the demon world) which when drawn returns Rin to his demon form. While in his human form, Rin exhibits a number of physical traits that are signs of his demonic nature, such as sharper-looking teeth, slightly pointed ears, and a black, fur tufted tail (which he keeps hidden in his shirt). As a demon, Rin gains two blue flames that float above his head, long, elf-like ears, and his eyes turn bright blue. In both forms Rin can almost control his destructive bright blue flames, the trademark sign of Satan. However, when he draws Kurikara, the magnitude of the flames dramatically increase and often leads to Rin being "consumed" by his own flames and losing his mind. Rin also has a demon Familiar Cat Sith, Kuro, who was initially Father Fujimoto's. He is surprisingly good with his hands, and his cooking repertoire includes all kinds of Japanese and Western foods (home cuisine). (Source: VIZ Media)

The heroine of the series, Alice first appears as a chain that persuades Oz to form a contract with her in the Abyss. In fact, she is actually the infamous B-Rabbit (Bloodstained Black Rabbit), the strongest chain in the Abyss. Alice's goal is to find her lost memories, which play a major role in the story. In human form, Alice has long dark brown hair with 2 side plaits. She has a huge appetite and loves meat especially. She is hotheaded, loud spoken and says what she thinks without regard to the consequence. Despite this, she has a soft side, especially when Oz is involved. She hates when Oz leaves her alone, but to hide it she usually says, "I'm in a contract with you. You are my manservant, and as a manservant, what were you thinking, leaving me behind!?" or she just hits Oz and says, "Shut up."