The Emperor's digestive tract is the only part of his insides that is explored, which runs from the top of the Emperor's throat to his stomach, where Blight is found. The walls are a fleshy mixture of pink, red, and light yellow, but they become greener and the air fills with green mist as the stomach is approached. The only notable feature is the Emperor's uvula, which may be struck to exit his body.
Blight took up residence inside the Emperor sometime before Amaterasu's arrival and took control of his body. The demon forced the Emperor to imprison Kasugami in a gourd and place Kaguya in prison; eventually, the poisonous mist formed by Blight's presence forced the Emperor to be confined to his bed in great sickness. The mist began to spread from the Emperor's mouth, filling Sei'an City and passing its sickness to the city's residents.
After making their way into the Emperor's bedroom and traversing the rafters, Amaterasu and Issun dropped down into the Emperor's mouth to find the source of the green mist. Making their way to his stomach, they encountered the tiny demon Blight and the sword that controlled it, Goldnail. Amaterasu, using her new Celestial Brush technique Veil of Mist, soundly defeated Blight and Goldnail, purging the Emperor's body of the green mist and, therefore, cleansing the city and its inhabitants of the sickness.
Realizing that Kaguya was still in prison due to the Emperor's demon-influenced order, Amaterasu and Issun took control of his body, moving him around with a jerky walk. After passing by several soldiers, who were shocked to encounter the Emperor up and about, the pair had Kaguya released before exiting the Emperor's body.