Primary

• Takayuki Furuichi Friend of Tatsumi Oga

Extended

• Tatsumi Oga contracted to Kaiser de Emperana Beelzebub IV
• Tatsumi Oga Classmate of Aoi Kunieda
• Tatsumi Oga Classmate of Hajime Kanzaki
• Tatsumi Oga Classmate of Shintarou Natsume
• Tatsumi Oga Classmate of Tatsuya Himekawa
• Tatsumi Oga Son of Oga's Mother
• Tatsumi Oga Son of Oga's Father
• Tatsumi Oga Younger Brother of Misaki Oga