It's nearly time for the Saikai Academy ball sports tournament, and Yukina and Nagisa are all fired up to act as cheerleaders! And thanks to the workings of Motoki and Rin, Kojou and Asagi are paired up to participate in the badminton doubles match for their class. Meanwhile, Natsuki is occupied with the capture of some therianthropes that have appeared in the warehouse district, and someone is targeting the Fourth Progenitor again...

Kojou and Yukina meet Dimitrie Vatler, a nobleman who shows an abnormal degree of affection toward the Fourth Progenitor, and Kirasaka Sayaka, Yukina's old friend also under the employ of the Lion King Organization. When Vatler proposes that Kojou capture some terrorists hiding out on Itogami Island and Yukina volunteers to take care of them instead, Vatler challenges Yukina to test her suitability for the task. And, though Sayaka has always been a friend of Yukina's since childhood, her behavior starts to change...

In her excessive defense of Yukina, Sayaka launches an attack on Kojou, but he can't control his powers. Yukina's arrival prevents the situation from growing dire, but Yukina leaves them both on the school roof to think about what they've done.

Gardos the terrorist has reawakened the ancient weapon, Nalakuvera. Kojou and Sayaka barely escape with their lives, but they fall into the depths of the manmade island. Asagi hurries to analyze and control Nalakuvera while Yukina fights a fierce battle to stop Gardos.

The trouble with the Black Death Emperor Faction has been resolved. Kojou has returned to his daily life with Sayaka as a new acquaintance, but he can't decide whether or not he should reveal his vampiric nature to Asagi. It's around that time when he meets a friend of Nagisa's, Kanase Kanon, known as the middle school saint.

Still stuck in Yuuma's body after the mind switch, Kojou rushes to see Yukina and the other girls. At first they're unsure whether to believe him, but after an explanation, Kojou and Yukina try to locate Yuuma in Kojou's body as they draw closer to unraveling the mystery of the witch of the void.

Yuuma's goal was to use the Fourth Progenitor's magic power to free her mother from the prison barrier. In accordance with her plans, the prison barrier appears above the ocean's surface near Itogami Island.

Kojou comes out of the battle with his own body back, but both Yuuma and Natsuki have fallen. The true prison barrier has been revealed along with Yuuma's mother, Tokoyogi Aya, and the other magic criminals who were incarcerated within.

Kojou and company search for Natsuki, whose spiritual powers were stolen by Aya's grimoire and is now missing. Just then, Yukina's surprised voice directs the others' attention to the TV, where Asagi is seen on the live broadcast of the Halloween Fest...

Kojou and Asagi take Sana on board Vatler's boat, the Oceanus Grave II, to protect her from danger. But Kojou's relief is short-lived as he is soon accosted by Vatler's beautiful young maids, and his stimulation is pushed very close to the limit when he ends up sharing a bath with Asagi...

Through Sana, Yukina sees a memory of Natsuki and Aya ten years ago, and then dreams of a happier world she shares with Kojou, Sayaka, and their friends.

"Goodbye, Himeragi..." After hearing Kojou say this to her in a dream, Yukina begins to contemplate her future and the coming of the day when she may have to leave Kojou's side.

Shortly after Yukina lost the use of Schneesturm Wolfin and received an order to return to the Lion King Organization, Itogami Island begins to fall apart under attacks from a magical beast that consumes dragon veins.

Lucas and Polifonia discuss the abduction with security. Meanwhile, with the two abductees bound and gagged nearby, erstwhile maid and now full-time terrorist Trine Harden discusses their plans while humiliating Kojo. The world is oblivous to the abduction which is kept from the public. On the day of the ceremony, at Trine's command, Kojo boards and takes over the Aldegyrian flagship, the Bifröst.

Myriad forces continue to converge on the frozen Lake Kannawa. Asagi and Lydianne, riding in the pink tank, are joined by Ibliss, a high-ranking vampire from the Warlord's domain, after he rescued them from flying demons. Gajou and Shio carry the comatose Nagisa across the frozen lake, seeking a haven for her.

Shio defies Azama. From afar, Shirona incapacitates the lower level cultists. Okiyama appears on a wyvern and leading a second one to retrieve Azama and they flee. Azama joins the other confrontation and first betrays Ueyanagi, transforming him into a golem, and then attacking Yuiri, triggering a distraught Glenda to transform and fly off with Yuiri, Kojo and Yukina.

Kojo and the others go to rescue Asagi, who was imprisoned on the 0th floor of the Keystone Gate. Kojo is worried about Himeragi's poor condition, but Himeragi goes with Kojo nonetheless. What was waiting for Kojo and Himeragi on the 0th floor?

Kojo and the others are helpless by the power of Meiga Itogami's Cleansing ability. Kojo wonders what the hell this Cleansing ability is. At that time, the truth about the Cleansing is passed on to Kojo. Will Kojo be able to protect Himeragi and Itogami Island from Meigawa Itogami?!

Kojo goes to Iblisveil Aziz in search of answers on how to defeat Veres Aladar, but Iblisveil only gives Kojo a vague answer. Kojo returns to the agreed place of the duel shorthanded and begins the duel.

Kojo wakes up at Natsuki Minamiya's house. On TV, Asagi and Vatler appear to be working together and declares war against the Holy Ground Treaty Organization. In addition, Asagi says that Grenda will use Cain's legacy that she has protected as her power, to help save Itogami Island. Meanwhile, to save Nagisa, whose life is in danger, Hektos tells Kojo and the others that she will need to hold a ceremony.

With the help of La Foria and Veres Aladar, Kojo broke into the council and declared Itogami Island as his territory as the 4th Primogenitor and gained the right to veto the attack. But for him to be recognized for this, he must expel Vatler from the island and become a true ruler. Can Kojo defeat Vatler, who has absorbed the power of the Cleansing, and save Itogami Island from the crisis?!