The premise of Tenchi Muyou! Ryououki: Heian Muyo! has Aeka, Yosho (in his Katsuhito form), Tenchi, Mihoshi, Ryou-Ouki, and Ryouko in the Heian era (794 AD to 1185) of Japan. Tenchi and Mihoshi are samurai partners on their way to slay a demon, while Aeka longs for Tenchi's return.