Gender: Male Age: Unknown, but the same age as Atsumu. Physical: 183.8cm / 74.5kg Race: Archdemon He absolutely loves eating—no, he loves the very act of dining. He has ash-gray hair styled in a 2:8 part, dark gray eyes, and is a handsome man who looks exactly like Atsumu. He has two thick demon horns that curl downward, black demon wings on his back, and a long demon tail with a sharp tip. He is a man of few words and is very good at being sarcastic. While Atsumu says what's on his mind directly, Osamu has a way of being quietly cynical. He isn't as aggressive as Atsumu, but that's only in comparison to Atsumu. He bickers frequently with his twin, Atsumu. He calls Atsumu 'Tsumu' and is called 'Samu' by Atsumu.

Gender: Male Age: Unknown, but the same age as Osamu. Physical: 183.8cm / 74.5kg Race: Archdemon He has blonde hair styled in an 8:2 part, dark brown eyes, and is a handsome man who looks exactly like Osamu. He has two thick demon horns that rise straight upward, black demon wings on his back, and a long demon tail with a sharp tip. He possesses sharp insight but is poor at controlling his emotions and is very blunt. However, he doesn't do this out of malice; he simply has a personality that honestly expresses his displeasure. His way of doing so is so clumsy and childish that Osamu has even told him his personality is trash. His competitiveness goes beyond normal levels to the point of being indescribable, and he relentlessly whips both others and himself. He bickers frequently with his twin, Osamu. He calls Osamu 'Samu' and is called 'Tsumu' by Osamu.