After going on their journey, Bokka and Sayako arrive in a town called "Bakuyagou", or "White Night Cape", where it's always dark, and morning never rises, making it a perfect place for tourist attractions. It also seems like whenever the mysterious lighthouse shines red, no child appears on the streets, for they fear that their children would be killed by something. Bocca came to ask a knowledgeable lady about Melos Warriors. Bocca also found himself saving a young girl, Kew, from a robot creature, who was conveniently a little sister of the owner of an inn, who allowed them to stay for the night, as a debt. The two travelers knew there was something wrong with the city, since the residents didn't seem like they wanted to be saved or anything, even though there was something as dangerous as the robot creature. What lies in store for them? What is wrong with White Night Cape?

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.

Although knowing the problems of White Night Cape, Bocca continues to try and destroy the Monster Union robot creature. Everyone in the town knows of his intentions, and sends Bocca into jail. Sayako finds out that Kew knows about Keiko siding with the Monster Union, and saves Bocca from jail. Even with Sayako's warning, Bocca still calls for his Aiba-Machine and tries to save Kew from her sister's hands. The battle of Bocca vs. Midnight Fledgling begins.