Angolmois: Record of Mongol Invasion - Season 1 Episode 7 Kanatanoki

In a flashback, Emperor Antoku gives the High General of the Genji Forces, Minamoto-no-Kurō-Yoshitune a short sword. Back in the present, the Emperor recognizes the same sword carried by Jinzaburō. Teruhi then arrives and is welcomed by her great-grandfather the Emperor who gives her a message for the Magistrate Nagamine of the Toibarai - to protect Sasu and the capital. Teruhi swears to protect the island, but her Sō clan are unhappy about relying on the Toibarai. When the survivors arrive at Aso Bay, they find the Toibarai women abalone divers have led a small seaborne advance party of Mongols into a trap, killing them all. They also discover that the invaders are composed of many different groups, and these are Jurchen. Teruhi gives Nagamine the message from the Emperor, and he agrees to help her, taking the Sō survivors to their castle, Kanatanoki. First built 600 years earlier, the Sō discover the castle is well-fortified and supplied, however Jinzaburō declares that it is too big to defend with the limited forces they have.