Hearing what Subaru had to offer, everyone else in the room reacted to his words, with Wilhelm giving the biggest reaction. When they questioned the information's authenticity, he pulled out his cell phone, letting Russell look it over to get a merchant's opinion. Making sure not to let Crusch see through his bluff, Subaru explained that the cell phone would help in locating the Hakugei, fortunately getting a confirmation from Rem to further his claim.
At that moment, Anastasia arrived, causing him to get straight to the topic, telling Crusch that his information would help in her planned subjugation attack on the Hakugei. Hearing his claim, Crusch questioned him about it, as a claim like that would be considered slander if false. Recalling the various bits of information he heard across his various lives, he gave his opinion, which ultimately turned out to be correct, leading Crusch to accept the alliance. Following the formation of the alliance, Subaru, Crusch, Anastasia, and Russell discussed their plans, as they had to get everything done within 30 hours before the beast itself appeared. Following the discussion, Wilhelm approached Subaru and thanked him for his help, revealing that his surname was actually Astrea, which he claimed he already knew, causing Crusch to point out that he was lying.
Once the discussions finished, everyone got to work to prepare for the attack, except for Subaru, who didn't know what he should do. When he voiced his thoughts to Ferris, he corrected his thinking, telling him that it wasn't "his fault" but rather "thanks to him" that everyone was able to fight the Hakugei. He then began to tell him a little about Wilhelm's past, though unfortunately for him he was told off for doing so, nonetheless Wilhelm elaborated a little on it.
Twelve and a half hours later, Ferris had Subaru choose an Earth Dragon to ride, and despite having no experience in picking between various ones, he chose a proud looking one which surprised Rem, who informed him that the type he chose were known to be unsocial and feared that his hand would be eaten. Returning to the large room, he got to know some of the members of the attack force, such as Ricardo Welkin, before Crusch herself joined them. Subaru offered to use himself as bait to direct the Hakugei, as his scent would attract it, and she agreed to it after seeing that he wasn't lying. At that point ten people arrived, all above 50 years of age, who thanked Subaru for allowing them to fight the Demon Beast, as they were all victims of its powers. Soon after, before Crusch began the meeting, Subaru discussed a deal with Anastasia and Russell which would come into effect after the beast was defeated. Once Crusch's meeting finished, the members of the attack force made their way to Flugel's Tree at Lifaus Highway, where the Hakugei was scheduled to appear.
On the way to the tree, Subaru got to know Mimi and Hetaro Pearlbaton, discussing the plan a little with them, then gathered his resolve to fight. Seeing this, Ricardo moved over to his Dragon Carriage to chat with him, during which he revealed that instead of Earth Dragons the members of the Fang of Steel rode Ligers, a type of beast that was similar yet different as it specialized in nimbleness instead of power. As he left, Rem noted that he was doing his best to try and get the members to relax. The group continued on, reaching their destination five hours before the scheduled time, where they finished all their preparations for the battle the following day.
Taking advantage of the free time before the battle, Subaru and Rem visited Flugel's Tree, marveling at its huge size. While there, Rem revealed that she knew the cell phone wasn't a Demon Beast alarm, nevertheless she promised to keep quiet about it, even if he couldn't explain to her why he was lying, because she believed in him. Despite knowing her feelings, he still mentioned that he loved Emilia, however this made her tell him that she was fine with being a second wife. He told her that he would accept her offer if Emilia allowed polygyny, prompting her to tell him that she would try her best to convince Emilia to accept.
A while later, the attack force gathered together when it became close to the scheduled time, though when the Hakugei appeared, Crusch's agitation made her miss the timing for an order, causing Subaru to shout it instead with Rem attacking the beast with her magic. The two ran off on their Earth Dragon, prompting Crusch to order the others to follow suit, and the rest of the group began attacking the beast. As they moved to their planned location, Rem, who was in her Oni Form, told Subaru to look down to prevent himself from being blinded by the Night Clearing, which was formed from a large number of light stones joined together to form an artificial sun. Spotting them, the Hakugei began to give chase, allowing the others to keep on attacking it, eventually forcing it to lose altitude due to its wounds, enabling those with swords to reach it. Despite their attacks, the Hakugei didn't lower its altitude any further, however Wilhelm managed to carve out its left eye along with inflicting damage to its body, causing it to release a massive amount of mist from the mouths across its body.
Covering the area with its mist, it began using its secondary Mist of Elimination to fight back against its attackers, succeeding in eliminating twenty one people, all of whom were forgotten by everyone except Subaru, who theorized that he was able to remember them because of his ability. The mist forced Crusch to order the use of one of the two Evil Repelling Stones they had, immediately clearing the mist from the area, as the mist was the beast's mana, yet at that moment the beast let out a roar which incapacitated a large number of people. Fearing an attack while they were incapacitated, Subaru decide to resume his job as a decoy, using his attempt to talk about his Returns by Death to deepen his witch smell and guide its attention to him. As he did so, he heard a voice tell him that it loved him, and was seized by strong emotions, but they disappeared when he returned to normal.
Just as he expected, the Hakugei set its sights on him, continuously chasing after him, and didn't show any signs of stopping even after Rem tried to slow it down by launching spears of ice at it. The others helped by attacking it, causing it to climb up into the air, and then released the Mist of Elimination above, raining down a torrent of deadly mist down onto its attackers. Most of the group managed to escape the attack, still some were swallowed up by the mist, never to be remembered again. Soon after, Wilhelm was swallowed up by the Hakugei from behind, while Ricardo was blown away with a strike from its tail, with Subaru despairing when he realized that there were now three Hakugei attacking them. As the others began to lose hope, Rem attempted to save Wilhelm from being swallowed, and upon seeing this, Subaru regained hope, declaring that he wouldn't let this stop him. Quickly joining Rem, he helped her fight against the Hakugei that ate Wilhelm, using himself as bait once again to distract it while she attacked it.
The beast, flailing around in pain, almost hit him with its tail, however Mimi saved him with her magic, thanking him for helping the others regain hope. The two encountered a different Hakugei, which attempted to hit them with its mist, though fortunately Crusch forcibly shut its mouth with her magic, joining them right after. She thought it was strange that they never heard that the Hakugei created groups, ordering him to find out the truth, then raised the others' morale by pointing out that Subaru was trying his best. Returning to the Hakugei that Rem was fighting, he acted as a decoy again, then moved to return to the Hakugei that Crusch and the others were fighting against, all the while trying to think of a reason why there were now three Hakugei. Mimi and Hetaro joined him to protect him, with Hetaro informing him that Ricardo had noted that the one that hit him was lighter than normal, and after some thought, he realized what was happening. Running past the Hakugei Rem was fighting against, he noticed that it didn't have a left eye, coming to the conclusion that the Hakugei had split itself into three, its power also split between all three of them.
Suddenly, the Hakugei that was chasing him began rubbing its body against the ground, and following a combined attack from Mimi and Hetaro, the bottom bulged then ripped apart, letting Wilhelm out along with a torrent of blood. Regardless of his injuries, Wilhelm tried to fight on, prompting Subaru to have the two Cat Beast Humans take Wilhelm to Ferris while he returned to Crusch to report his findings. Discussing the newly gained information, he theorized that the reason the third Hakugei didn't join the fight was because it couldn't afford to be killed, then told them about a plan he had to attack it, requesting their assistance to do so. Using a large spear of ice, Rem launched him into the air inside of it, sucessfully delivering him onto the beast's back. He jumped off the beast to try and get it to chase him, and when it restrained itself from following, he told it that Rem died because of it, causing the shadowy hands to appear, along with the same voice which told him that it loved him.
The Hakugei, unable to restrain itself for a second time, dived after him with the intention of destroying him, but before it could reach him, Rem used ice spears to attack it, slowing its descent enough to allow her to retrieve him. The Hakugei smashed head first into the ground, nevertheless it tried to chase after Subaru, which he took advantage of by leading it right into the path of the falling Flugel's Tree that Crusch and the others had prepared in advance. The force from the falling tree was enough to pin it to the ground, yet wasn't enough to kill it, prompting Wilhelm to finish it off, shouting his love for his wife after dealing the finishing blow. Seeing that the Hakugei had been killed, everyone celebrated their victory, happy that the battle was finally over.
After the battle, Subaru rushed over to the injured Rem, worrying about her condition, as she had protected him from the shockwave formed from the force of the tree smashing down onto the Hakugei. She soon regained consciousness, however she was in terrible condition, and after seeing this, he accepted her request to tell her that she loved him. He also agreed to let her be with him in the future, telling her that he wouldn't give her to anyone, causing her to reveal that she wasn't dying at all, with Subaru soon realizing that she had tricked him into saying all of the things she requested. They were then interrupted by an amused Ferris, who he realized had been listening to their entire conversation right from the beginning.
Ferris teased him about it until Crusch appeared, at which point she and Subaru talked about the aftermath, explaining to him that they needed to take the Hakugei's dead body to prove that it was dead. Calling him a hero, she thanked him for his efforts in the battle, offering to add him to her camp, an offer he refused as he couldn't betray Emilia, and instead she promised to remain friendly with him even if they had to fight against each other as part of the election later on. Hearing that Subaru had something else he needed to do, Wilhelm offered to help him, and to Subaru's surprise Crusch ordered Ferris to go with them to honor their alliance. Ferris accepted her order without question and took around twenty members who were still able to fight. Surprised that Ferris agreed to go with him that easily, he questioned him about it, to which Ferris pointed out that he didn't doubt Crusch's decision to trust Subaru, quietly letting go of his dislike toward him soon after. Ferris then told Rem that she was going to stay with Crusch, prompting her to protest his decision, but calmed down once Subaru told her that she didn't need to worry about anything.
Splitting off from Crusch's group, Subaru, Ferris, the Fang of Steel members, and the rest regrouped with the other half of the Fang of Steel, which included Julius, as he was Anastasia's knight. When Ferris complained that he didn't help fight the Hakugei, Julius corrected him by claiming that he was "Yuri", as a knight working as a mercenary was dishonorable. After exchanging insults with Subaru, he thanked him for stopping the Hakugei, causing Ferris to point out that Wilhelm was the one who killed it, however Julius pointed out there wouldn't have been a battle against the beast if it wasn't for Subaru. Following his thanks, Julius asked whether he was going to keep on using the Fang of Steel or not, leading Subaru to recall what Petelgeuse had said about the Hakugei, telling Julius that the Hakugei was connected to the Witch Cult, which he deemed to be enough to continue with their assistance.
Feeling guilty after seeing that Julius was quick to understand the situation, Subaru apologized for his actions during the discussion about the election, prompting Julius to also apologize for holding him in contempt for what he did. Later on, before dawn, Subaru discussed their next objective, which was to prevent Petelgeuse and the Witch Cult from massacring everyone in the village and at Roswaal's mansion.