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Yushiro and Miharu follow the long-lost Path of the Kai to the threshold of Kyoto, home to the lost secrets of Yushiro and Miharu's past. Upon touching the threshold, the two young kais are given a glimpse of Japan in the Heian period, around 1,000 A.D.. The story tells of a disagreement in the Watanabe clan, the last protectors of the secret of Gasaraki. This disagreement leads to the accession of warlord Tsuna Watanabe who intends to use his clan's kai, Yushiro and Miharu, to reassert its power in the face of centralizing imperial power.

渡辺の地にたどり着いたユウシロウとミハルは一人の老人と出会う。老人に促されて骨嵬の像に手を触れた二人に古からの記憶がよみがえり、意識は平安時代へと遡る。その時代、影で朝廷を支えてきた渡辺党は、骨嵬を差し出せという朝廷からの命令を巡り内紛状態になっていた。