If Yasuda's assumption is true, it is highly probable that he was mobilized because of the connection between samurai in the imperial capital, that is, the fact that he was a child of roto (allied troops) in Kyoto.
仮に安田の想定通りであれば、京における郎党（同盟軍）の子弟という、京武者コネクションでの動員の可能性が高くなる。