Two days after Michikatsu's betrayal of the corps, Muzan and another demon frantically worked around a table inside a room within the Dimensional Infinity Fortress where a partially demonized Michikatsu was laying. He had been receiving injections of Muzan's blood over the past two days and nights, and so far, they had kept him alive and healed his wounds. They also modified his body, resulting in him now possessing six eyes as opposed to just two. Muzan had just finished what would be his final injection, which would also wake him up from the coma Muzan had induced him into to keep him stable. "Now," Muzan told him. "Rise from your slumber, Kokushibo."

Michikatsu had now completed his transformation into the demon known as Kokushibo. As he opened his eyes and found himself strapped down to the table, he took a few deep breaths and asked him, "Muzan-sama… How am I?"

"You look absolutely wonderful," Muzan told him with a smile. "You have attained a great power, far beyond any demon slayer."

"Wait," a demon asked. "He can say your name?!"

"Of course he can," Muzan spat back at him with anger in his voice and in his eyes. "He's my greatest creation yet! He gets privileges none of you cretins get!"

Kokushibo then turned his head as best as he could in his restraints and asked Muzan, "Wait, where's my wife? Where's Tenko? Is she safe?"

Muzan's smile faded as he sighed. "I'm so sorry, Kokushibo. It appears that she passed away. You accidentally killed her. Your children have been taken from you too." In reality, he was only feigning sympathy for him. On the inside, he felt some joy from Tenko's death, knowing that now, there was nothing to tie Kokushibo down.

"What… No!" Kokushibo could not believe what he had just heard. "No, she can't be dead! She was alive, and I felt it! I could feel it! My children shouldn't have been taken either! I can't be all alone!" Sadness and anger at himself for his actions flowed through him as he began to moan in both physical and emotional pain. He then began to fight his restraints, eventually managing to break them and roll off of the table onto the floor.

A demon yelled as he tried to grab a hold of him, "What's he doing?!"

"Let him go," Muzan ordered him.

The demon then felt a growing pain inside him as Kokushibo's anger grew further and he let go of him. "Wait… What… What's happening to me?!"

Muzan turned to him and told him, "You've outlived your usefulness. Nobody else must know of the procedures we used on him." He then snapped the fingers on his right hand.

"What the fuck?! No, please, don-" The demon then explodes into numerous pieces, splattering blood everywhere as Kokushibo finally began to rise from the floor.

"That's it," Muzan told him. "Arise, my servant!"

"No…" As he came to his feet, tears flowed from all six of his eyes, his grief overcoming him before he screamed up at the ceiling, "NOOOOO!" Michikatsu Tsugikuni was now completely dead, and in his place, Kokushibo had killed him and occupied his body with the help of Muzan Kibutsuji. The scream he had uttered was the last little piece of his old life finally escaping him, and with that, there was no turning back.

Muzan then told him as he continued to weep, placing a hand on his shoulder, "I'll leave you here to process your grief. When you are finished, we have work to do."

…

Ten days after the battle with Michikatsu, Yoriichi was on the road. All of his friends had abandoned him and denounced him for his failure to kill Muzan, the fact he kept Tamayo alive, and his failure to stop his brother. He was angered by their accusations of cowardice and treachery, even more so since they knew he was still mourning the loss of his students and his sister-in-law. For the time being, he had found temporary refuge with Tenko's family, who had agreed to take him Michikatsu's twin sons and raise them as Tokito family members. Alongside him was Tamayo, who had turned to drinking blood she gained voluntarily from others, mainly Yoriichi, to sustain her. The two remained strictly platonic, both still trying to process the previous week and a half's worth of events.

At night, the two slept in the same room down in the basement of the house, but not together. Tamayo stayed in the basement during the day, and would walk up to the rest of the house at night if needed. As Yoriichi read one of the few books that survived the fire at his old house, Tamayo asked him, "What are you reading?"

"A book about the history of the corps," Yoriichi replied to her. "Me and my brother composed it. We had just finished it a few months ago before everything happened. It was one of our passion projects. It was left on the ground in front of the house, which was odd."

"Maybe he pulled it out of the house before it burned completely."

Yoriichi sighed. "I want to believe that, but… With everything that happened, I find it hard to truly believe it." Changing topics, he then asked her, "So, I didn't ask you this before to give you some time to think about it, but what exactly did Muzan make you do?"

"What he made me do?" Tamayo sighed. "That…" As anger seeped into her voice, she looked down at the floor. "That bastard made me sleep with him, and no, not actually sleep."

"He had sex with you?"

"Yes," Tamayo replied. "Do you think I was in a position to say no to that asshole?"

"Good point," Yoriichi agreed.

"That fucking little… Ugh, he was so disgusting. He wasn't even good at sex."

"Good at it?"

"Like… He couldn't please a woman if one threw themselves at him." Tamayo chuckled. "I'm just trying to find some light in all this. I still feel dirty from being with him."

"I'm sorry."

"Don't feel bad," Tamayo insisted as she got closer to him. "Please, don't feel sorry for me. I literally ate my family. I feel like I deserved it."

"You had no control over yourself," Yoriichi replied with a soothing tone. "It wasn't your fault, Tamayo. It was Muzan's fault for tricking you. You didn't deserve any of this."

"Yoriichi…" She then closed his eyes and leaned in for a kiss, which Yoriichi suddenly found himself returning almost subconsciously. The two locked lips for quite some time and even wrapped their arms around each other before Yoriichi split off from her. "I… I'm not sure about this. My heart still feels like it belongs to my wife."

"Mine still feels like it belongs to my husband," Tamayo replied as she gently pushed Yoriichi down onto the bed. "But I can't hold it in anymore. Something's telling me to do this."

Yoriichi realized he felt the same way, and kissed Tamayo again before he began to reach into her kimono to undo it. She replied by reaching into his clothes as well, the two now deciding to go all the way together. He then split from the kiss and told her, "I want to feel something again."

"Then make love to me," Tamayo answered him as she untied her kimono and let it slip off of her. "Wait, no… Fuck me, Yoriichi."

…

Two days later, Yoriichi would say goodbye to his in-laws as well as Tamayo in the late evening. He desired to move throughout Japan to keep Muzan off of his trail, and he believed that staying in one place all the time would only put others needlessly at risk due to the giant target Muzan had probably painted on his back. Downstairs in the cellar, he packed his things, including his sword, as Tamayo asked him, "Am I coming with you?"

Yoriichi paused for several seconds before telling her, "No."

Tamayo was shocked. "Wait, why?"

"I don't want any harm to come to you," he replied. "I've already made arrangements for you to stay here with the Tokito family. They're more than happy to let you stay."

Tamayo walked up to Yoriichi and hugged him from behind. "But… But I need you, Yoriichi."

Yoriichi sighed. "What we have between us… I don't think it's love, but rather us trying to feel like we belong after our true loves were taken from us." He then turned around to find tears streaming down her face. "I barely know you, Tamayo, but… A small part of me wants to stay with you, too. Even so, I know I would only put you in harm's way." He wiped the tears from her cheek, as he told her, "Don't cry for me, Tamayo. Make the life I gave you your own. Help humans and demons alike. Help us defeat Muzan and bring peace between our peoples."

"Yoriichi…"

The two then shared one last kiss as they closed their eyes and embraced each other. When they split, he said, "One day, I will return to you."

"I'll be waiting for you," Tamayo promised. "I'll never forget you, Yoriichi."

…

Upstairs, Yoriichi talked to Tenko's oldest brother, a man named Akimasa Tokito, as he finished packing. "So," Akimasa told him. "I intend to raise my sister's kids as if they were my own. I'll make sure of it."

"Thank you, again, for doing this," Yoriichi replied with relief. "Make sure those kids get the care they need. They've been despondent ever since their mother died and their father became a demon."

"We've all been grieving," Akimasa replied with a hint of sadness in his voice. "It's hard having to bury your own sister far before she became old."

Yoriichi then finished wrapping up his last bag of things he needed to go on his way. "Well, this is goodbye for now. Please, keep her kids safe, Akimasa-kun, and make sure Tamayo's safe, too."

"Absolutely," Akimasa replied as the two bowed to each other. "It would be an injustice to my sister if I didn't."

Later on, as Yoriichi left the house, Akimasa, his wife, his own three children, Tenko's two sons, and Tamayo watched him leave as darkness fell onto the area. Uncertainty surrounded everyone involved, but there was a small feeling of hope within the despair of the situation that had befallen everyone. Yoriichi had made his intentions clear to continue to teach the Breath of the Sun to others, even if it was under a different name to keep himself and any potential students of his safe. Despite being exiled from the Demon Slayer Corps, he vowed to keep up the fight as an independent slayer, even if it meant having no protection from a larger agency and no reliable means of backup.

The fight would continue on.