Zenki is the main character of the Japanese anime series Zenki. He is a demon guardian spirit that fights agains the evil forces of Karuma.
In episode 5 of the Zenki anime, Zenki and Chiaki do battle against Ikaku, a gluttonous man-eating demon that has possessed the principal of Chiaki's school. Zenki is permitted by Chiaki to transform into his "adult" form so that he can fight the monster. During the battle, Chiaki is nearly eaten by Ikaku, which gives Zenki the idea that, if Chiaki were gone, she would not be abe to revert him back to his "child" form. Consequently, Zenki grabs Chiaki and willingly feeds her to Ikaku. Shortly after Chiaki is eaten, Zenki is enveloped in an aura of light and is transported into Ikaku's stomach.
Inside Ikaku's stomach, Zenki meets back up with Chiaki who explains that she used her bracelet to summon him. After the two bicker for a bit, Ikaku's stomach acids begin to rain down on them. They realize they must destroy Ikaku's weak point, which is inside his stomach. Zenki locates and attacks the weak spot, which destroys Ikaku and releases both of them from his stomach.