The title says Trilogy because this game was intended to be the first installment of the three, however the sequels 2nd 夜叉”神"魔牙の専横政策 (Yaksha "Jin" Maki's Tyrannical Policy) and 3rd 夜叉包囲陣、帝都崩壊! (Yaksha's Siege, the Imperial Capital Collapses!) were never released.