Keikei is a little boy who lives in a rike with his older sister, Rangyoku, and Enho. He and Rangyoku originally came from the Wa Province and their parents died late in the reign of Jokaku, when all the women of the country were being exiled.

When the new ruler of Kei ascends the throne, Keikei is especially excited about the good news. He and his sister settle down in the province of Ei, where Rangyoku helps Enho with household tasks. When their rike is attacked by youma, they are saved by the arrival of Chuu Youshi, a young woman who has come to study with Enho. Keikei and Rangyoku quickly become her friends.

(Source: wikia)