Born from the stone egg of Mount Huaguo, Son Goku (played by Ainosuke Kataoka) wreaks havoc in the Heavenly Realm, earning the wrath of the Jade Emperor (played by Shin Tamura) and is imprisoned under the Five Elements Mountain.
The story of Mairimashita! Iruma-kun follows Iruma, a kind-hearted 14-year-old boy whose parents sell him to demons for their own selfish interests. However, the demon he is sold to has no grandson of his own, so he dotes on Iruma and sends him to demon school.