After recognizing Elizabeth and the Seven Deadly Sins and regret that Zeldris remains attached to Gelda as Meliodas to Elizabeth, everyone understands that they are not talking to Meliodas but to the Demon King. Zeldris demands his father explain why he is in the body of his brother after having told him to crown him as his successor, leading the Demon King to reveal that he never intended to give the throne to his treacherous son and that what he really wanted was a young and strong body.
After being surrounded by Elizabeth and the Sins, they demand that he leaves the body of Meliodas. The Demon King declares that he will free Elizabeth from his curse, but only to be able to kill her brutally, wondering what face Meliodas will put on him when he sees his corpse and if he will become depressed and want to join her in the afterlife or perhaps relieved of not being held back for her.
The Demon King attacks Elizabeth, but Gowther saves her, while Merlin put anyone who could not fight under the protection of Perfect Cube. King, Diane and Mael attack the Demon King with physical attacks knowing that magic would not work against him, but the Demon King easily defends himself from all their attacks and send everyone flying away with a simple movement of his claw-like limbs. He states that any resistance is futile and that Elizabeth should let him end her miserable life for good. Hawk begins to provoke him and warns him to not kill Elizabeth. The Demon King destroys the little Perfect Cube where Hawk was in with his claw, heavily wounding him, saying that he is very irritating and that he will send Hawk to where his brother is. However, Hawk is snatched just in time from his clutch by Ban, who appears on the battlefield and boldly declares he will take the Demon King out of the Captain's body. The Demon King sarcastically asks him how he intends to get him out, which Ban responds he will simply do. King warns him that even with his immortality, taking this enemy would prove difficult. Ban leaves King shocked when he reveals to him that he is no longer immortal, as he revived Elaine with the power of the Fountain of Youth.
Calling him a fool, the Demon King says he will show him the power of a god and releases a toxic and caustic storm over the entire area, destroying the rest of Camelot castle. King protect his friends with Pollen Garden, while Gowther believes that no living being could survive that. Ban, however, endures it without problems, calling it a gentle breeze when compared to Purgatory. The Demon King tries to attack him with his claws, but Ban uses his speed to dodge and punch him in the face, but the Demon King manages to block it, having to stop his storm in the process. The two then enter a physical contest, going blow for blow. The Demon King however manages to strike him in the stomach and back, making Ban to kneel down. The Demon King says that he was a fool believing he could do something against him by his own.
However, something seems to suddenly affect the Demon King, to which Ban says he is actually not alone. Everyone can feel a presence from within Meliodas' body: the emotions of Meliodas returned to confront the Demon King inside his heart, in a spiritual world. The Demon King says that even if he managed to return, he will not let him do what he wants, since bringing death and fear is his duty and his own existence. Meliodas evades his sword and elbows him to knock him down, claiming that THAT is his sin.
While regretting not destroying them both in Purgatory, the Demon King delivers a flurry of attacks against Meliodas and Ban, that are completely evaded by both of them. Meliodas confronts him with a sword of darkness, while Ban kicks the Demon King in the head, smashing him into the ground.
The Demon King reminds Meliodas that after his body awakens to the power of the Demon King, the latter could no longer be in the real world for more than a day, but Meliodas affirms that is okay as long as he can break the curse of Elizabeth and say goodbye to the Seven Deadly Sins. Meliodas cuts off his chest and one of his helmet horns. The Demon King tries to lie to Meliodas' to make him lose hope, claiming that there is no need to look for Elizabeth, as she is already killed after the curse was broken. Meliodas does not believe him but cannot avoid contemplating that possibility, making him drop his guard, because despair in the mindscape leads to drowsiness and eventually sleep. The Demon King takes the opportunity to slash him multiple times with his sword.
While in the real world, Ban seems to have the upper hand, even managing to smash the Demon King's head into the ground with strength enough to produce long cracks in the ground. Ban then taunts him saying that his power is nothing compared to the real Meliodas. But as the Demon King slashes his son in the spiritual world, the King regains strength and grabs Ban by the neck with his claw and pierces his abdomen with just his fingers.
Elizabeth and the Sins try to reach to Meliodas to help Ban, but the Demon King tells them that their voices will never reach him to where he is. Suddenly, Gowther tells everyone that he has a plan.
In the spirit world, the Demon King tells a badly beaten Meliodas that embracing the despair in that place is equal to accepting death. As Meliodas is losing consciousness, the Demon King maliciously tells him to give up because there is no one out there waiting for him. In that moment, Elizabeth and the Sins, who entered the spirit world thanks to Gowther's magic, appear to support Meliodas, refuting the Demon King claims. Infuriated by their presence, the Demon King attacks with the intention to eliminate them. However, Meliodas is able to repel his attack and knock him down, puncturing his chest with small dark spheres and leaving several holes. The Demon King asks how is he able to have that power. Meliodas states that since his friends' existence and emotions have given him strength, the Demon King has lost any chance of defeating him.
In the real world, the Demon King suffers the damage of Meliodas' attack. After violently throwing Ban away, he decides to cut off his son's power source by taking out at once Elizabeth and the Sins whose physical bodies were immobile while under the magic of Gowther. Mael and Ludociel jump in to protect them, but the Demon King mocks them saying that the Archangels have no right to challenge a god. Then, the Demon King releases his claw-like limbs and sends them upwards to the sky. They are transformed into a great face-like creature called Tansoku no Kenjin. Ban quickly uses Snatch to slam the creature into the ground. The Demon King sends him flying away with an elbow strike, ordering everyone to stay out of their family affair with his son. The Tansoku no Kenjin recovers and then releases a powerful blast from its mouth, devastating much of Camelot. Ludociel manages to use Sanctuary to protect himself along with Mael, Hendrickson, Elizabeth and the Sins, but the Demon King says that nothing will be left of him in five seconds. From within the explosion, Ban appears, and while the Tansoku no Kenjin continues to shoot magic blasts, he resumes the fight with the Demon King, but now appears to struggle to keep up with his attacks.
Out of the blue, Zeldris intervenes and stops the Tansoku no Kenjin by piercing it with his sword and undoing the spell, leaving everyone surprised.
The Demon King asks Zeldris for the reason of his actions. Zeldris tells him that he wants him out of his pending affairs with Meliodas, but before that he asks him if he knew about his relationship with Gelda when he ordered him to execute the Vampire Clan. With obvious disappointment, the Demon King says the he is just a fool for not understanding that he did it to save Zeldris from himself and his own weakness. He reveals that the Commandment that he bestowed upon him revealed everything about his secret love with Gelda, the sealing of the vampires and Zeldris' hope to reach the throne of the Demon King to create a Demon Realm in which everyone could live in peace, something that the Demon King considers pathetic. The Demon King states that Zeldris' loyalty was what saved him all that time, but he will no longer turn a blind eye. He then creates Setsuna no Inja, a spell creature, to take care of Zeldris, while the Demon King continues his fight with Ban.
Meanwhile in the spirit world, the Demon King spirit is being overpowered by Meliodas, who uses several concentrated darkness spheres to penetrate his armor and flesh. Meliodas tell his friends that they just being there have give him strength, and with the promise of getting back and reunite with them, Meliodas sees them out. After giving their final words of encouragement, Elizabeth and the Sins leave. The Demon King is completely overpowered by Meliodas' relentless attacks that destroy his sword and knock him down. Meliodas declares to end the fight with the next attack.
In the real world, Zeldris keeps fighting with the Setsuna no Inja and is somewhat wounded by its sharp blades and fast movement. He reflects on his relationship with Meliodas and the path he took, then musters the strength to use Ominous Nebula and obliterates the creature. Zeldris turns to his father and ask him to get out of Meliodas' body. In response, the Demon King shoots a energy bolt that cuts open Zeldris' chest, seriously wounding him. As an astonished Mael points out that magic is not supposed to affect Zeldris, the Demon King reminds everyone that that was a power that he lent Zeldris. As Zeldris falls, wounded, he entrusts Meliodas with the future.
Ban, who was pinned down by the Demon King, takes the chance to recover and kicks him in the face. Ban furiously strikes the Demon King, claiming that Zeldris is his own flesh and blood. The Demon King hits him back stating that he does not need weaklings in his bloodline. Ban gives another strong blow leaving him dizzy.
At the same time, Meliodas uses his last attack, Trillion Dark, to hit the Demon King with a myriad of darkness spheres.
At the doors of his demise, the Demon King begins to bounce across the battlefield in the real world in a state of madness, in a desperate attempt to take Meliodas to the death with him. Ban manages to intercept him and then, with a kick, sends him flying up. Elizabeth, Merlin and King then simultaneously use Ark, Perfect Cube and Pollen Garden combining the techniques into Triple Prison, trapping the Demon King inside a layered enclosing sphere. However, he manages to break free with ease, now in a berserk state. Energy accumulates in the Demon King eyes, in an attempt to use a powerful attack, but Hawk jumps on top of his head and block his eyes with his hooves to hinder the blast, though he can not avoid being fried by it. Then, Diane uses Diamond Tower to produce a massive pillar from the ground that hits the Demon King, pushing him upwards. Ban takes the chance and quickly climbs the pillar, leaping into the air and then delivers the final blow to the Demon King, smashing him through the pillar all the way to the ground.
With the Demon King removed, the Demons attacking Liones begin to retreat while at the battlefield, Ludociel begins to disappears in Mael's arms, who explains that even though the Seven Deadly Sins had succeeded in driving the Demon King out of Meliodas' body, the Holy War has not truly ended, only being the first step towards the reconciliation of the Goddesses and Demons after hating each other for so long.
Unknown to everyone, Cusack and Chandler awaken shortly after the Demon King is driven out of Meliodas by Ban and find the Commandments expelled from his body as well as, to Cusack's horror, Zeldris in a crippled state from his father's attack. Chandler plans to leave him to die but Cusack immediately kills his counterpart to prevent him from saving Zeldris by making off with his pupil as well as the Commandments themselves.
Hidden away in a cave, Cusack forces Zeldris to absorb all of the Commandments to save him, without realizing that he has allowed the Demon King to return to the physical world in Zeldris' body. After possessing his second son, the Demon King does away with Cusack and mocks Meliodas for failing to destroy him.