Pinkamena found that two weeks had gone by since the meeting of the Hashira and Kagaya, informing their leader that Upper Moon Six had been defeated, and, despite some criticisms from some of the others, she had been introduced to the higher echelon of the Corps without delay. She was the 'Chaos Hashira', on account of her unique Breathing Style, and, as such, they would have given her one of the white jackets that some of the others wore, even though Tengen didn't wear one, but since she was so unique they decided on a modified kimono. It was being built with the materials that went into making the attire of a Demon Slayer, much like what she was used to wearing, and there was an area being added so her tails could slip through, both pony and fox alike, with the chest section being blue, the legging section being red, and the sashes that went with it were black. Based on what she could tell it was designed around her Nichirin Blade, since it was blue with some red spirals, so she said nothing and found that it was also altered slightly so the fabric wouldn't get in the way whenever she fought the Demons that she was hunting.
Mitsuri, the Love Hashira, claimed that she was the 'Kitsune of Hope', meaning that she and several of the others saw her as a beacon of hope in their war with the Demons, so she didn't argue with them and accepted the attire when it arrived, only to find 'Chaos' written in Kanji on the back, much like the attire that the others wore.
Her official jurisdiction was Tengen's domain, since he had retired from being a Slayer and was taking up being one of the few Cultivators who existed across the entire island, so her first order of business was figuring out the border of her zone and setting up a net with her power. Such a thing was invisible to everyone and wouldn't block anyone from entering or leaving her part of Japan, rather it was designed so she could track down any Demons that intruded upon her domain and allowed her to track them down, which would improve the lives of the Humans under her care when she took one out. She found that most of her targets were minor Demons, nowhere near Daki, Gyutaro, or even Akaza possessed, but that didn't stop her from taking them out whenever she could do so, even though she paid attention to what the crows said, leaving the ones that had been assigned to the other Hashira alone. When Pinkamena wasn't busy tracking down Demons she trained inside her Mindscape, allowing her to maintain her skills and ready her for whenever she found a tough foe, even though Akaza and the other Upper Moons seemed to be avoiding her, if they knew about her existence and what she had done to two of their members.
While she did that, however, her friends remained in the Butterfly Mansion, as while Nezuko had helped them survive with minimal injuries, especially when one considered the fact that Pinkamena had stopped Gyutaro in his tracks, the three of them had used too much energy and pushed themselves to the brink, so it would be some time before they woke up and resumed their duties. Of course when she thought about that it wasn't exactly totally true, as Zenitsu was already awake, in fact he was being sent out more often than before and he hated it, but Tanjiro was fast asleep and Inosuke was slowly recovering on his own, so it would take some time before they got up. Nezuko, from what they could tell, was just fine and she slept while she waited for her brother to wake up, though Pinkamena and Shinobu, or whoever was on hand, checked on her when the sun went down, since the sun still hurt her and they weren't about to put her through that. Such a thing didn't stop Pinkamena from gathering a vial of her blood and sent it along to Tamayo, as she was sure Tanjiro was eager to find out what was up with his sister, given the transformation she went through when they fought Daki, and it might be another key to solving the mystery the Demon doctor was currently working on.
After some time she received an unexpected arrival, a crow that was followed by Obanai, something that actually caused her to raise an eyebrow for a moment, as all the messenger had to say was that Kagaya wanted to make sure Obanai had some company for the mission he was about to embark on.
"I can understand why you were recommended to become a Hashira, even though I don't like it," Obanai said, where the two of them departed from the Butterfly Mansion and headed to the west this time, allowing them some time to talk and observe the scenery, though it was easy for Pinkamena to see that he didn't like her at all, in fact he seemed to hate most of the people he interacted with, "but I have no idea why you need to come with me. I can handle this mission on my own, without someone like you bothering me."
"Look, I get it, you don't like anyone, and you especially hate Demons, but Kagaya asked me to come along," Pinkamena replied, where she shared the Serpent Hashira's opinion, she didn't like him that much since he had bullied Tanjiro back when Sanemi stabbed Nezuko, but she was also willing to forgive and forget, which she was sure came from Pinkie, hence why she focused on the road, "think of it this way: if the Demon is endangering all sorts of Humans I can use a barrier to keep them safe, opening the way for you to deal with whoever our target is... I'm only here to protect the people that the Demon might be hunting."
Obanai glanced at her for a moment as he headed down the road, following a path that seemed familiar to him, telling her that he must have traveled the road a lot at some point in time, before deciding to ignore her entirely as his snake kept an eye on her, showing Pinkamena that it might not like Demons either. Neither of them said much as they walked, save for the fact that the snake's name was Kaburamaru, a companion that had been with Obanai for a long time, which was all he was willing to share with her, so she accepted it and focused on why Kagaya asked her to come with Obanai. As far as she could tell it could be a family matter, that a relative of Obanai's might have become a Demon and he was being sent to do the deed, regardless of whose domain the Demon was actually in, but even as she thought about that she could tell, just from a glance and what the others had told her, that most of the Hashira had lost their families. Of course Kyojuro was the lucky one, as his father and brother were around still, and Tengen had retired with his wives, but the others didn't seem to have anyone else in their lives, other than their subordinates and Kagaya, so part of her wasn't convinced that this was about one of Obanai's family members.
Based on what she could tell they were going somewhere that was near a road, so people wouldn't be suspicious, which turned out to be a large mansion that was in Giyu's domain, a place Obanai recognized as she could see the hatred in his eyes, including the dislike in his snake's eyes. That told her everything she needed to know, this had to be where he was born and had lived for a long time, a place he must have condemned after leaving it to become a Slayer, and that this had to be why Kagaya asked Pinkamena to join Obanai as he traveled down memory lane. The memories he had locked away must have come back, causing him to recall everything he had tried to forget, though as they got close Pinkamena found something that had to be different from what the past held, there were men and women who had wooden staffs in their hands, like they were guards or something. Obanai recognized that fact as well, which meant something must have gone down since his last visit to this place, especially since he didn't like what they were seeing right now, something that told Pinkamena that there had to be a Demon somewhere in this mansion, confirming the reports that the crows had told the two of them about.
As such she held a hand out, stopping Obanai before he revealed themselves to the Demon that was here, and focused her mind for a moment as she sought out the demonic presence that had to be here, where she found a pressure point coming from one of the higher rooms and suspected that the Demon might be Lower Moon material, even if Muzan had disbanded that part of the Twelve Kizuki.
"There's definitely a Demon in the mansion, in a large room based on what I can tell." Pinkamena commented, where she could tell that Obanai froze, no doubt recalling the section of the mansion she was talking about, causing her to focus on what might be waiting for them once they entered it's domain, allowing her to study the area before they made a move on their target, "I can set up a barrier to stop it from fleeing, and put the Humans to sleep so they can be transferred to my Inner World, where they won't be harmed by our foe, so you can focus on slaying the Demon."
Obanai turned his eyes to Kaburamaru for a moment, as he still wasn't sure it was wise to trust a Demon, before deciding that he might as well trust Tengen's judgement, for if she did something that sabotaged it he could take her down before telling the others about her betrayal, to which Pinkamena nodded and got to work. Not a few moments later he found that a circular barrier surrounded the mansion, something none of the guards noticed before they swayed and fell asleep, just as she said they would, and once she was done securing the area she gave him a thumbs up. With the coast clear, and the pair had nothing to fear from the Humans that had been here, they started to move inside the mansion, which happened to give Obanai a chance to see another aspect of her power in actions, the slumbering Humans were disappearing, which meant they were appearing in the duplicate mansion she had created in a matter of seconds, in her own world. It was the same as what Tengen had said, she made sure the people had a safe haven to rest in, even if they didn't realize they were being moved to the area, and when they were done clearing out the Demon she would move everyone back into place in a matter of seconds, to make it look as if nothing had happened.
Thanks to that Obanai wasted no time in traversing the mansion, heading up to the room he didn't want to be in, a room he would rather destroy and get out of his life, yet he knew it was where the Demon was lurking, and sure enough he had to pause by the sliding door of their final destination, before steeling himself for what was on the other side. What he and his companions found was a large room that was dazzling and overly luxurious, like it had been ripped from his memory or something, and on the opposite side of the room rested a familiar alter, where one would expect a statue to rest, which the people of the house would worship before going about their day. Resting in the middle of the shrine was a figure that was a near perfect copy of the Demon he had seen the previous Flame Hashira, Shinjuro, kill with his own eyes, as it was a female serpent Demon, as in everything from her waist down was that of a snake and the tail coiled around a young girl, who had likely just come of age, that was knocked out from the shock of what was going on. It was easy for him to realize why he had been picked for this mission, the Demon's layered black hair was exactly like his, only longer since hers went all the way to her back, her snake body was brass colored, not the golden color he recalled, and her face had taken on a more snake like appearance, reminding him of what happened to him in the past.
Of course this Demon was mimicking the older serpent Demon, as in she wore nothing over her chest and her breasts had three lines on them, matching what he remembered of the older female Demon, before he finally recognized the eyes that the Demon had, the stern blue that was filled with disgust for him.
"Cousin, so you return at long last." the Serpent Demon said, where Pinkamena could see that her tongue was longer than a Human's and was snake shaped as well, meaning she had left her humanity behind, while confirming the reason behind why Kagaya asked her to come with Obanai, since he was meeting a family member.
"After everything that happened, you went and became the very monster that slaughtered and ate who knows how many people, not to mention our twisted family," Obanai replied, though this time around it was far too easy for Pinkamena to hear the hate in his voice, meaning his cousin must have been a piece of work and combining her with a Demon that must have traumatized him when he was younger was just igniting the anger and hate he must have buried inside himself, but she kept quiet as she observed the pair, "you are no longer my cousin, Demon, and I will cut you down like the others I've fought over the years."
Pinkamena said nothing as Obanai flashed forward and swung his blade into the Serpent Demon's tail, slashing it apart as he avoided the girl his former cousin had been preparing to eat, though when he stopped it was by her and he dropped off the girl, where she quickly checked her and found that she was just fine, so Pinkamena sent her to where the others were resting. Of course, since they were fighting a Demon and pieces were falling, she also collected the tail sections that had been cut free and stored them away as well, while finding that the Serpent Demon had some decent regeneration, as she healed the cut parts in a matter of seconds before rushing at Obanai. It was clear, just from how he moved, that this was a fight he was going to drag out on purpose, venting all the anger and hate he had felt over the years at this Demon, a being who had once been his own cousin, but whatever kinship they had in the past was gone, replaced by the desire to fight and kill the other in a fight to the death. Part of her felt that this was just sad to watch, two family members forced to duel each other until one of them was dead, even if neither of them had seen eye to eye in the past, and the other part of her just wanted to blame this all on Muzan, who seemed to enjoy tearing families apart in his mad quest to become the perfect being, all so he could walk in the sun and rid him of his only weakness.
The only thing she was able to confirm was that the Serpent Demon was definitely a Lower Moon, in terms of power, but it didn't matter in the face of Obanai's power, who sliced his former cousin apart over and over again as the minutes went by, before he finally beheaded her and dropped the body to the ground, allowing Pinkamena to collect all of the parts, all while the other Hashira stood there in silence.
"Based on what I can tell, the people here were kidnapping people to feed to the Demon... we might be able to arrest all of them, with the girl's help." Pinkamena remarked, as she had been studying everything that was around the mansion and felt an underground area that seemed different from what a mansion would have, an area Obanai likely knew about, but she didn't pry into his past as she talked, while focusing on some skulls, blood arms, and a few blood spots they had both missed when they entered the area, "What do you think?"
"Go ahead. They deserve to rot in prison." Obanai said, his voice calmer than she thought it might be, after all the hate and anger he must have poured out in his battle with his former cousin, but at least it was out of his system and he didn't look like he was planning on doing anything drastic after finding out that one of his relatives had done all of this, copying what he had seen in the distant past.
As Pinkamena set things up, moving some of the Humans around so the innocent ones would realize the danger they had been in and the evil ones would be knocked out for a time, though since everyone else was asleep Obanai did something that surprised her, he actually talked about his past. Apparently this was his old home, where he had been the first male child born in a long time and, since his family was worshiping a serpent Demon that loved to feast on babies, he was kept around, but it was his eyes and looks that allowed him to survive for a number of years, until he actually met the Demon who would later kill his entire family. The difference between his cousin and the original Serpent Demon was that the first one had golden eyes and golden scales on the lower portion of her body, while his former cousin had blue eyes and brass scales, and, after recalling what he had seen, his cousin had been fifteen, maybe sixteen, when she became a Demon, all while the older one had been between twenty to thirty, based on their chest sizes, since his cousin's were smaller. The rest of his family served the Demon, robbing everyone they kidnapped, and, because the Serpent Demon liked him, they even cut his mouth to match her snake like maw, though he lived in fear during those years, found Kaburamaru, and escaped at long last, only to be saved by Shinjuro.
Following that event his cousin berated him for causing the death of their family, the Serpent Demon had done it in rage over him escaping, and he went on to become a Slayer to make up for all of the wrong his family had done, only for him to eventually discover that his own cousin took the Demon's place and was recreating his wretched past.
"Don't worry, no one will have to live through the pain you endured... and the others won't hear this tale from me, since it isn't mine to tell." Pinkamena remarked, all while she and Obanai walked out of the mansion that had once been his cage, as it wasn't right to call it his home, not after what he had told her, and he tilted his head for a moment, surprised that she would keep all of this a secret from the other Slayers, "Come on, let's set this plan in motion and put these kidnappers in jail, where they rightfully belong."
Obanai found that it went as Pinkamena said it would, the girl and the other kidnapped individuals found themselves in a scene that made it look like the kidnappers would eat them at some point in the future, as the Demon had arranged some of the parts with the pool of blood that remained of his cousin. That scene installed fear in each of them and caused them to flee without delay, though she had also arranged the kidnappers to make it look like they had fallen asleep after a meal, making it look like they were also cannibals, which would explain the eaten body parts. The pair remained on a hill that was near the mansion, where Obanai was able to watch over his old prison without fearing that someone might find out where they were resting, another benefit of her strange Blood Demon Art, and it wasn't long before the officials arrived to investigate the scene. Sure enough, as Pinkamena had said, the kidnappers were being hauled off to jail, as they had been found with evidence of them eating people, responsible for abducting others and holding them against their will, and even stealing from merchants whenever they had a chance, meaning they were going to jail for the rest of their lives.
It was a fitting punishment, given the lives they had destroyed to become rich and powerful, and all Obanai did was nod as he watched it go down, though once everything was said and done, and they were sure that the Demon's followers were being properly punished, the pair departed and headed back to the Butterfly Mansion, each looking forward to what the future held for them.