Conrad is made a prisoner when Francia join in alliance with the Demon Kingdom. As Conrad escapes from his cell, Yuri and the others chase him to hopefully discover the reasons for his betrayal.
Yuri's older brother Shori recalls when Yuri would call him big brother. Once Shori took his little brother to an amusement park, and little Yuri accidentally spilled his ice cream on a thug's pants.
A number of children gather for a celebration at Covenant Castle, including Hube and Nicola's son El, but things get crazy when El's magic powers are amplified by one of Anissina's devices.
A mysterious girl bearing a strong resemblance to Ulrike is being mischievous around town, and Yuri, Conrad and Wolfram must get her under control. Meanwhile, back in the Tomb of the Great One, Ulrike is unable to perform her normal tasks.
Stoffel plans to set Yuri up with an appropriate princess, thereby cementing ties with the current ruler of the kingdom. When Princess Elizabeth arrives, Yuri is faced with a battle between his current fiancé and the new princess.
Yuri and the others hear of a box at the bottom of a lake and go to investigate. There they meet a girl who turns out to be Urike's predecessor, who reveals that if they remove the box, the land will become barren
Gwendal despises Conrad's father Dunheely, but when they are faced with helping a secluded town of outcasts, Gwendal must learn to see his step-father as the person he truly is.
After their box is stolen by the Maou, Big Shimaron uses an overseas study exchange to impose power over the allied countries. However, The Great Demon Kingdom and the allied towns are not fooled.
Adalbert takes King Yuri hostage and demands to know if Yuri has Julia's soul. Big Shimaron's troops attempt to capture Yuri, and Adalbert comes to the rescue.
Panic engulfs the troops of both nations and Big Shimaron's king decides to abandon the children he has in order to escape the volcano's wrath. Adalbert decides to fight Conrad and unleash all of his pent up emotion.
Maxine still has hope of returning to his country and becoming powerful. He kidnaps Yuri in an attempt to escape, but runs into one of Yuri's devoted subjects and must abandon his plan.
Yuri stumbles upon the Demon Mirror and is transported back in time, actually meeting Lady Julia and discovering why she is so beloved. They watch as Conrad and the Luttenburg Division set out on a suicidal battle to prove their loyalty.
Gunter sets off on a Nation Wide Tour to bond with the Common People. He comes to a town modelled after the old west and finds it is full of fear, and the only person holding it together is a girl named Gloria.
A man cloaked in shadows arrives wielding the power of the holy sword, and the sword has been spotted in a series of bandit attacks. Yuri's followers suspect that Alford is behind these attacks.
Yuri and the others investigate the rumours about the Holy Sword and stumble upon a man possessed with demonic energy. Alford arrives looking for his sword and winds up helping Yuri and the others retrieve it.
A mysterious masked man with hypnotising powers enters King Belar's castle unhindered. Meanwhile, back in the Demon Kingdom, Yuri holds a party where faceless puppets attack and run off with Wolfram.
Yuri is captured along with Wolfram and taken to Big Cimarion to be handed over to a hypnotised King Belar, but their transport is attacked by bandits led by a familiar face. The masked figure sends demons to retrieve Wolfram and Yuri.
Yuri decides to try and convince King Belar to stop fighting and heads off for the King's Castle with Adalbert in tow. After many battles, Yuri arrives in the king's throne room and discovers that King Belar is being controlled also.
Ulrike reveals that the final box is on Earth so Yuri and the others set off to bring the box back to the Demon Kingdom. Yuri is shocked to learn that his family already knows about the other world.
Yuri takes the group on a sightseeing trip while waiting for Bob, the Maou of Earth to contact him. Rodriguez asks Shori to persuade Conrad and the others to return to their own world.
Yuri and the others travel to Switzerland after learning that Bob is staying there. Shori tries to persuade Yuri to stop being the demon king and come home.
With all four boxes gathered in one place, the animals of the Demon Kingdom get restless, and the Boneys are no exception, leading them to kidnap little El.
Gunter is poisoned once again and Suzanna Julia's retired father comes to the Demon Kingdom to release him. While he and Yuri talk of Julia, Gunter's body unexpectedly moves on its own.
One of the maid trio falls ill thanks to the effects of a strange miasma, and the only cure is a rare herb found on a mountain where the same miasma causes people to be unable to trust each other.
Yuri, Conrad, Murata, and Wolfram travel back to Earth to retrieve something Yuri left behind, but when they are unable to return to the Demon Kingdom, they travel to Switzerland to ask Bob for help.
A group of humans begin to rebuild a bridge that once linked their village to the Demon Kingdom before the war 20 years ago, but they get attacked by strange spirits; Adalbert and Gunter find themselves fighting side by side.
Gunter teaches Yuri the history of the Great Demon Kingdom, including the founding King Shinou, the Great Sage, and the four families with the keys to the boxes. Wolfram seems to be acting strangely afterward.
The lake in Switzerland pulls Shori to the Great Demon Kingdom by accident, and he asks Yuri to stop the ceremony of the forbidden boxes and questions the Original King's decisions.
A possessed Wolfram offers Shori magical powers to protect Yuri but before Shori can answer, an unexpected visitor arrives. Ondine's twin sister Seraphine is determined to destroy the keys so the four forbidden boxes remain closed.
Shori can now manipulate water, but loses control while practising. When Seraphine attacks Yuri at the temple, Shori defends him but his powers seem to take over his ability to show mercy.
Yuri forgives Shori and consoles him by admitting his admiration for using maryoku so quickly, while Greta calls him Uncle. They all head over to the Original King's Temple so Yuri can carry out the ceremony.
Yuri begins the ceremony but Wolfram suddenly attacks and a dark figure appears. It absorbs the power from the boxes and reveals the translucent form of the Original King.
Anissina believes that Wolfram is still alive and plans to freeze his body like Gunter's when he was poisoned. Yuri and everyone return to Covenant Castle to form a plan to defeat the Original King and save Wolfram.
Yuri and the others head back to the Original King's Temple to retrieve the keys, but are attacked by Soushu's army of dolls. On Earth, Soushu's powers attack the group in Switzerland.
Conrad, Gwendal, Jozak, Hube and Gunter wake up outside the temple and return to the castle, where Wolfram has been revived. In various countries, Soushu's shadows attack and Yuri finds himself in an empty house of his heart with Shinou.
The gang are shocked to find Murata saying Yuri now belongs to Shinou. An attempt at using Yuri's blood as a key transmits a vision of Julia into Yuri's soul, where she shows him all of his past acts of courage and tells him he can save everyone.
Soushu is forced out of Yuri's heart, causing his troops to disappear as well. Murata tells Yuri that they won't be able to travel between worlds again, and there is just one portal left.
