Melody of Oblivion

The Vinderlize intends to destroy the Mitranome. Child Dragon utilises a weapon that can immobilise the Aibar Machines. And the secret of Project Silent is revealed.

The Meros warriors are on the Mahoroba and on a course to Mitranome. But the space port is guarded by the monster union and they intend to stop them.

The kidnapped prime minister is interrogated by the Armed Theatrical Group. The prime minister reveals his intended deal with the Monster Union. He also mentions about his lost daughter. The origin of the new Monster King is also revealed.

Tone and Sayako are held hostage in the tower. And Coco and Bocca have gone in to rescue them. However, Shuuma has explosives planted all over the castle and he will not hesitate to set them off.

Bocca and Sayoko arrives at a tourist spot. Sayoko's investigation into the place reveals that several tourists have gone missing there. They spot the body of Tone's Aibar machine, Skyblue, the blue eyed boy, lying close to the waters. Bocca revives him with the aid of his Aibar machine. They learn that Tone has been taken prisoner at a castle managed by a member of the Monster Union known as Lucky Thoroughbred. Skyblue suddenly warns them that they had been spotted and that the enemy was headed their way. Flying Bunny, a girl in a bunny costume riding a flying board, arrives. Bocca, Sayoko and Skyblue are spotted by her. She goes on an aerial attack. In the battle against Flying Bunny, Bocca's Aibar machine attempts to fly but is unsuccessful. Bocca successfully wounds Flying Bunny, and she retreats to the castle to heal herself. She meets with Lucky Thoroughbred and they exchange some harsh words. Lucky Thoroughbred reveals his intent to set bombs all over the world and then visits his captive, Tone. Skyblue meanwhile, meets up with another Airbar machine, the one who uses boomerangs as weapons. They fight each other. Sayoko meanwhile tries to kiss Bocca, but Bocca hesitates. Sayoko learns why, she realizes that Melody is watching them. Sayoko runs off feeling hurt. She is suddenly greeted by Lucky Thoroughbred in his monster machine. Sayoko however, looks more surprised than afraid. And instead calls him, "brother".

In this labyrinth, where space and time can be curved or warped, Bocca is able to meet with the child sacrifice, Solo, as well as Kurofune. Bocca witnesses the battle between Horu and Kurofune that happened in the past. Horu was defeated but was able to survive by hiding in the labyrinth because of the warped time. Bocca parted ways with Kurofune and later got separated from Solo, so he wanders off by himself in the labyrinth.

Bocca and the team successfully saves Sayoko. Sayoko reveals to them that there are still people in Engine One. They decide to try and save them too. The Monster Union member is later defeated in battle, but reveals that the people aren't really 'humans' but have been turned into something better. Tsunagi, in his attempt to destroy Engine One from the control station, finds a recording of someone he knew and had thought betrayed him. The recording reveals some surprises. Bocca wants Tsunagi to leave the place with him before the whole place blows up, but Tsunagi insists on staying. The team leaves without Tsunagi, and Engine One blows up.

Bocca and Sayoko arrives at a huge industrial region. Sayoko befriends a strange girl by the name of Coco. Coco tells Sayoko that she is involved in a theatrical play nearby. Bocca and Sayoko later meet up with a guy who offers Bocca a job as a security guard. And while Bocca faces a team of saboteurs of the delivery truck that he is protecting, Sayoko is taken prisoner by the guy, who reveals himself to be a member of the Monster Union. Bocca's bow is damaged during battle, but his Aibar machine provides him a more stronger bow. As the battle goes on, the saboteurs which includes Coco, realizes who Bocca is and stops the battle. They show Bocca the contents in the truck and brings him to see someone he knows.

Bocca learns that the girl who had aimed her arrow at him is named Tone. And she appears to hate Melos Warriors. He also learns that the technique that she uses to drive the "working mouse away" is a Melos technique. However he notices that she has no stigmatic mark on her arm. On learning of Tone's return to the valley, Miri Kanaya becomes agitated and recalls back her earlier years, of how and why she joined the Monster Union. The relationships between her, Tone, Eichi Hikoyama and the blue-eyed boy are also revealed.

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.

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 Serenade, is unhappy with his high school life. And wants to become a warrior like the ones from the story told to him by Tsunagi.