Bocca finally learns that the robot creature he fought before was from the organization, Monster Union, who are humans who serve under the monsters, using the robot creatures as their weapons.Keiko Hamasaki, the sister of Kew, and the owner of the inn, remembers her past, and is reminded of why she joined the Monster Union. Later, the robot creature strikes again, and Bocca is faced with it again, giving Bocca a great surprise.
生け贄の女の子"キュウちゃん"を襲ったのはモンスターではなく、モンスターに使える人間達「モンスターユニオン」の仕業である事を知るボッカ。
そして謎のロボットを操る「モンスターユニオン」のエージェント"ミッドナイトひよこ"の正体はボッカ達のよく知る意外な人物であった・・・。
