Battle of the Shoya Kōji Siblings
The Battle of the Shoya Kōji Siblings occurred in 1515 in the southern portion of Hokkaidō. This battle was waged between Kakizaki Mitsuhiro and the Shoya Kōji siblings, the chiefs of the Ainu (Emishi) peoples.
In 1513, Matsumae-Ōdate, a mansion, fell and the lords, Aihara Suetane and Murakami Masayoshi, died. There are various theories whether this attack was initiated by the Ainu army or, rather, the forces of the Kakizaki clan. In any event, afterwards, the Kakizaki entered Matsumae-Ōdate. Meanwhile, Mitsuhiro demanded Andō Hirosue acknowledge him as the new military governor of Matsumae. Initially, Hirosue refused. Later, a compromise was reached on the condition that a majority of the levies collected for marine commerce by native Japanese visiting the Ezo territories and travelers be given to the Hiyama-Andō clan.
Uprising by the Shoya Kōji siblings
In 1515, the Shoya and Kōji siblings, chiefs of the eastern portion of the Oshima Peninsula, launched an attack against the Kakizaki clan governing the southwest portion of the same peninsula. The details are scarce. Mitsuhiro, aware that he was outnumbered and confronted by intrepid warriors, plotted to deceive and kill the Ainu by pretending to reconcile and holding a banquet with saké, inviting the chiefs to his base at the Matsumae-Ōdate mansion. He made the visitors drunk and pretended to show them valuables so they would drop their guard. He also arranged for the pounding of a wooden mallet to conceal the sound of preparations. Then, at the right moment, he assaulted them from behind a staged door. Mitsuhiro slayed the Shoya and Kōji siblings with a sword while other Ainu people were slaughtered by Kakizaki troops. The sword used by Mitsuhiro at this time was a family heirloom that his father, Takeda Nobuhiro of the Wakasa-Takeda clan, received from Kakizaki Sueshige and manufactured by a renowned swordsmith from the Kamakura period named Rai Kunitoshi.
The two chiefs of the Ainu were buried near the mansion and mounds built for their heads called the Emishi burial mounds. Until the era of Kakizaki Suehiro (Mitsuhiro’s grandson) when peace was made with the Ainu based on ordinances governing the transit of commercial vessels, forces from the Kakizaki clan who attempted to attack the Ainu were said to have heard faint voices from the Emishi burial mounds.
There is a theory that the battle was the result of a plan by the Kakizaki clan against the Aihara clan who at the time were based at the Matsumae-Ōdate mansion.
Issues regarding the names
The meaning of Shoya Kōji is not certain and the subject of several theories. Shoya Kōji appear to be the first names of two individuals who served as co-chiefs of the Ainu but could be the name of a single person as the representative of the Ainu, family names, tribe names, or even a place name.
Issues regarding the dates of events
Prior to these events, in 1496, the Mobetsu mansion of the Andō fell to the Ainu army while its lord, Andō Iemasa, fled to Kaminokuni, the base of the Kakizaki clan in the Hiyama District. Moreover, three mansions (Usukeshi, Shinori, and Yokuramae) in the southeast portion of the Oshima Peninsula were toppled by the Ainu army and the three lords (Kōno Suemichi, Kobayashi Yoshisada, and Kobayashi Suekage) died. According to records of the Matsumae domain, this battle occurred in 1512, but based on excavations of the Shinori mansion, the remains are deemed to be from the first half of the fifteenth century while traces from the sixteenth century were not found so the years do not align. In addition, the three lords who died are believed to be the children of Kōno Masamichi and Kobayashi Yoshikage who died in the Battle of Koshamain, a conflict between the Yamato people of Japan and the indigenous Ainu that occurred in 1457 on the Oshima Peninsula. This means the reign of those lords would be too long and is inconsistent with the date that their fathers died in the Battle of Koshamain.
According to certain sources, it occurred in 1519, but that would be after the death of Mitsuhiro, so 1515 is the more convincing date.