Yamada was a Nihon-Ja Senshi Lord who was manipulated joined Arisaka's Army.
History
Yamada was the lord of one of the Senshi Clans, it is not known what clan he commanded. It is known, however, that he is fiercely loyal to Shigeru and the legitimate heir of Nihon-Ja's Throne. Yamada and Shigeru were apparently acquainted, but Yamada (possibly due to his slightly short-sighted eyesight) would only recognize Shigeru at a close distance. Shigeru obviously respected Yamada and trusted him, suggesting that Yamada, unlike many Senshi, did not view those of the Senshi sect as superior to the common folk.
The Emperor of Nihon-Ja
Arisaka deceived Yamada by misinforming him that an impostor of Shigeru was in Ran-Koshi. Yamada, believed Arisaka's lie and he lead his army to Ran-Koshi to reinforce Arisaka's forces. Arisaka was loosing the battle as Shigeru's forces were causing heavy casualties to his army. But Yamada arrived and was ready to destroy the "Impostor". As Yamada's clan arrived with the intention of destroying the 'traitor', the Hasanu Army also arrived. Shigeru offered truce to Arisaka and Yamada, and proved to Yamada that he was the emperor and not an Imposter. Yamada, who was totally loyal to the legitimate ruler, told Arisaka that he would not let Arisaka usurp Shigeru's throne. Shigeru offered renunciation of the throne, leaving the choice of next Emperor to those like Yamada and Nimatsu, but Arisaka did not accepted the offer. Matsuda Sato, an officer of Arisaka's army, noticed that his leader was an usurper and a traitor. He shouted "Shigeru!" and soon many of the Senshi, Kikori and Hasanus joined the shouting. Arisaka impaled the officer and attempted to kill Will with his Katana, but Will killed Arisaka by throwing his saxe knife in Arisaka's neck. Yamada most likely returned to his castle after Arisaka's defeat, though remains unknown what happened to Yamada, the Senshi Lord.
References
- The Emperor of Nihon-Ja - Page 385