The mysterious entity simply known as the "Blue Demon" (青鬼, Ao Oni) is one of the two Appetite Demons residing within Toriko, the other being its counterpart, the "Red Demon". Unlike its counterpart, Toriko himself did not know of its existence until it was awakened during his battle with Heracles; the only beings who were aware of it were Ichiryu, Mansam, Chichi and the aforementioned Red Demon. Born from Toriko's appetite and given form by his Gourmet Cells, the Blue Demon exists deep within Toriko's subconscious, being sealed away due to its dangerous personality and level of power.