The war rages on, and Natsu, Gray, Lucy, Juvia and Happy continue fighting the enemy soldiers. Natsu's flames are, however, suddenly frozen as Invel makes his appearance. With everyone frozen solid but Gray, a fight between him and Invel ensues, with the former showcasing his Ice Devil Slayer Magic, much to the Spriggan's surprise. That is when Natsu and others break free from Invel's ice. Although, before anything can happen, Brandish appears in form of a giant, and takes everyone but Gray and Juvia away. Invel uses this to his advantage, and binds the two together with Ice Lock, forcing them to kill each other. Eventually, Juvia is thought to die from giving her blood to Gray in order to save him, subsequently enraging Gray to chase after Invel. After brutally beating him, though, he learns that E.N.D. is none other than his friend, Natsu.
Meanwhile, Lucy attempts to reason with Brandish, but to no avail, as she enlarges Natsu's tumor back and then proceeds to fight Lucy. This is stopped by Dimaria, who appears to call out Brandish on faking the fight and takes her down for being a traitor. She then moves to Lucy, blaming her for this turn of events.
Later, as Lucy regains her consciousness, she witnesses Natsu tied to a chair right in front of her, unconscious. Tied up and unable to use her Magic herself, Lucy is a target of Dimaria's hatred for what happened to Brandish, intending to torture Lucy before killing her. After a series of time-stops, which appear rather as teleportation to Lucy, she threatens both Natsu and Lucy, until she returns to the latter, preparing to gauge Lucy's eyes out. This causes Lucy to lose her consciousness yet again. Waking up shortly afterwards, Lucy finds herself on the ground, covered by blood. Looking around herself, she witnesses a scene of destruction, with its focal point being a shocked and beaten up Dimaria crashed into a wall. The culprit is revealed to be Natsu, as Dimaria mumbles about a monster that is capable of ignoring her ability: E.N.D. It is revealed by Porlyusica that the tumor is not what they thought to be, and Brandish enlarging it yet again caused something to awaken within Natsu. In the meantime, Natsu is seen rampaging near the repositioned guild building. As he searches for Zeref, he burns any and all enemies that stand in his way, until it is Gray who bars his way.
Upon seeing Gray, all Natsu does is asking him to let him go, with Zeref being the only thing he's thinking about. Gray attempts to talk to him, wanting to confirm if Natsu really is E.N.D. However, Natsu talks about nothing but killing Zeref. Disappointed, Gray takes this as a confirmation of Invel's words, beginning to imagine how his greatest rival is also his greatest enemy, responsible for all the darkness in his life. Reassuring Natsu that this is the end, Gray activates his Devil Slayer Magic, promising to kill him here and now.
Covered in dark flames that transform his arm into a demon-like claw, Natsu charges at Gray, with the Ice Mage ready to take on his attack. As such, the two clash in a fit of rage on both sides, destroying a huge area around them with their attacks. Gray gets ready to deliver another punch, but Natsu counterattacks, opening Gray's wound on his side. The Demon then strikes the Ice Mage with an exploding stream of flames just as he yells out that he cannot be stopped anymore, recalling Lucy's motionless body, which started his demonic rage. Gray responds with an equal amount of rage, intending to defeat and kill Natsu.
Afterwards, both Natsu and Gray stand in front of each other, exhausted. After a short while, Natsu charges once more, striking Gray, who attempts to defend himself with a shield of ice. Natsu eventually breaks through it and Gray is thrown into a nearby rubble. Nevertheless, he already has a counterattack of his own ready: the parts of the shattered ice shield are shot towards Natsu like projectiles, with the Fire Demon dodging several of them and subsequently destroying the rest with his flaming attacks. While that happens, Gray sets another plan into motion: he tries to stop Natsu from moving by freezing his foot and then shooting a beam of energy towards his opponent; Natsu is thus thrown away, tumbling backwards until he is able to stop himself. With no hesitation, Natsu responds with a strike of his own, sticking his demonic arm into the ground, which causes an eruption of flames at Gray's location. With a movement of his hand, Gray freezes the stream of flames coming from underground, but with no success, as all of his surroundings begin exploding around.
Gray thus focuses on getting rid of all the explosions, unaware that Natsu's next move is a roar attack, something that hits Gray with full force. The Demon then uses his flames to propel himself towards Gray, something which the Ice Mage anticipates and defends against with an ice wall, with Natsu crashing into it at full speed. Natsu tries to move around it, but Gray eventually closes him in with ice walls and launches a finishing attack: huge spikes of ice in Natsu's icy prison. However, Natsu escapes by jumping up, blowing up the prison of ice and launches himself towards Gray yet again. After a huge explosion that their clash causes, Natsu and Gray focus even more power into their fists, but, just in time, their subsequent clash is stopped by Erza, still crushed by Makarov's demise. As she appears between them, she questions the actions of the two.
Seeing Erza's tears, a shocked Natsu recalls his desire not to ever see her cry again, something which even drove him to crush Jellal back then. Similarly, Gray remembers himself fighting for Erza's sake, so that she can be happy in Fairy Tail. Erza tells them to recognize the comrade standing in front of each other and, through Makarov's words, reminds them of Fairy Tail's moral rule: a place where fighting because of hatred is not acceptable. Just as Natsu and Gray cancel their respective states of power, Erza embraces both of them, saying that she loves them. That is when Gray hears Juvia's voice, and turns around to see her walking towards him, supported by Wendy and Carla. Realizing that she is alive, he falls down, completely exhausted and, even though Juvia rushes to his aid, she is met with the same fate, with Carla commenting on repercussions of overexerting herself. Being in a similar state, Natsu slowly loses consciousness, just to find himself supported by Lucy, who arrives, worried about her friend.