Extremely long chapter.

Reader POV

Muzan stood in front of my children, all of which were tied up.

"So after all this time you really thought I wouldn't find you?" Muzan walked towards me, a gleam in his eyes.

"Mommy!" Sora tried struggling out of Muzan's grip but the restraints only tightened against his tiny body.

"Ah, and on top of abandoning our children, you run off and have a bastard child with one of my demons!" Muzan scoffed. "Pitiful."

I glared at Muzan. "What do you want."

"You know what I want. You are to be by my side soon enough. We will discuss soon enough though. Fear not, Dear (y/n)." My ex-husband's cold hands touched my face lightly. "One of my demons will transport you to my hideout. There we will talk."

And he was gone.

I could not contain the rage I felt and as I walked towards my children, the air became extremely cold as ice grew on the walls.

"That bastard. That fucking bastard." With one quick motion the three children were freed but I did not hug them.

No, I was positively raging.

"(y/n)?" Doma looked at me with concern.

I slowly turned my head to him. "Did you tell him."

"What-"

"Did you tell him."

I could sense his hesitance and knew he did. "Gyutaro, take your siblings and go to your rooms."

"But-"

"Now."

Gyutaro scurried away, Ume picking up Sora who looked like he was about to cry.

"Mommy! Don't be mad! Papa didn't do anything!"

My frosty glare broke and I gave him a sweet smile. "Sora dear, why don't we talk later? Papa and I have to talk now."

Doma nervously followed me out of the castle after I placed heavy protection charms all around the castle. "(y/n)-"

"Zip it." I was positively seething with rage.

He only used you.

He doesn't love you.

He was only keeping you around to report back to Muzan!

As these negative thoughts clouded my mind, a huge part of me couldn't help but wonder if they were right.

I stepped inside a magic circle said to be closed off to any spirits or demons-except the people inside.

"Doma. You're going to tell me right now. What the fuck was that?!"

He looked truly upset and tried to reach for my hand, which I instantly moved away. "I had no choice. He would've killed Michikatsu!"

"Michikatsu hasn't seen his father anytime soon!"

Doma shook his head. "That's where you're wrong. We had an upper moons meeting quite recently. The entire 12 Kizuki know Kibutsuji-Kamado Michikatsu-who goes by Tsugikuni Michikatsu."

Days later, I decided to go hunting for the son of a bitch husband of mine that I did not love nor ask for.

"Do you have to go?" Doma asked me as I stood outside in the pouring rain, my hands bloody as I had went on a rampage.

Even though I was mad at him, he deserved to know.

I nodded, licking some of the blood off my hands but spitting it out immediately in disgust. "Human blold is so fatty. Why do you kill them so much?! There are better substitutes."

"Animals. Really?! You do realize humans are animals?"

I ignored him and knelt down to the children. "You remember what I told you, right? If anyone asks if Doma and I are demons-"

"We say nothing!" Ume cheered, not understanding the danger.

Gyutaro seemed to understand and bonked his sister. "Stop it, this is serious!"

The two began to bicker before I suddenly trapped them in a hug.

"Mom?"

"My precious children. I need you to be careful, ok? I feel as though our time together will be limited."

Ume hugged me tightly. "Where are you going?"

"To find the evil man who tied you and your siblings up."

Sora came out from behind his father and ran into my arms, crushing his siblings who knew better to complain. "I'll miss you, Mama."

"I'll miss all of you more than you know."

A huge cloud of mist covered the sun as I walked towards the village, a sword in hand just in case.

Yoriichi. Michikatsu. I got your letter. I will be heading to the swordsmith village.

I reached the village at dawn the next day, being rushed inside as the sun shone through the clouds.

"Mother..." Yoriichi moved towards me, hugging me tightly. "You really came."

"I did," I stroked my second born's cheek affectionately. "You two have grown."

Michikatsu moved towards me and gave me a hug.

I pray that Doma's warning was wrong.

You are still my son. My blood.

Unfortunately, that's when the trouble started once more.

Michikatsu betrayed us and I received word that the home Doma and I shared with our children was attacked.

I ran home quickly with Yoriichi at my side, both of us praying no one was killed.

When I entered the home, I saw Ume in the snow, surrounding her was blood.

"What happened..."

"She and Gyutaro protected Sora," Doma explained as he motioned towards Sora who was crying in his arms, begging his father not to let go.

"She...she almost died. Had it not been for me turning them into demons-"

I whipped my head and looked at him sharply. "You did what?!"

"It was the only way!" Doma pleaded.

I cradled Ume's head, shaking my head. "I wanted them to grow up as humans. To have human children. To grow old and to embrace their lives to the fullest."

"But they would've died!"

"You know healers! Now they're going to forever be young! They'll never know what it's like to grow up or..." I shook my head in sadness and anger.

"Mama?"

My rage was stopped temporarily when Sora called out to me, his rainbow eyes pleading me not to be mad.

"Sora. Go with Yoriichi."

My second born looked down at his younger half-brother and his gaze softened. "You are my younger brother, aren't you?"

"Yes. Mama told us about you and Michikatsu," Sora whispered. "Why is Mama mad?"

I looked over at Yoriichi then back at Doma. "Yoriichi, bring your brother. We're leaving."

"What?! What about Ume and Gyutaro?"

Doma gave me a glare. "Just go. You made it clear you don't want them anymore now that they're demons like us."

"What? Not at all-"

"Leave. Every time something becomes an inconvenience to you, you run." Doma's voice was laced with dripping venom.

I looked at him with pure anger. "Excuse me?"

"I said what I said, (y/n). Every single time the going gets tough, you run away like a coward." Doma turned away. "Sora. Come."

My son with Doma gave me a heartbroken stare. "I don't want to. I want to stay with Mama."

"But Mama-"

"Zip it, Doma." I pointed a finger at him. "You're vile. Goodbye."

"So fucking dramatic. Fine! Leave!"

"I will!" I nodded to Yoriichi who gently guided his youngest brother away.

I'm sorry, Ume and Gyutaro. I can't be with you. The second I came back, my suspicions were only confirmed. You two are mere puppets for Doma and Muzan's plan. I'm sorry.

And I left as rain poured down, drenching the three of us.

____________

All around me was the infinity castle but I knew I could easily overcome the 12 moons of Muzan.

I saw only the upper 6. One being my biological son and the two children who I took in.

And Doma.

"(y/n). You look different." Doma's rainbow eyes shimmered with emotion but he didn't dare put those words into his mouth. "Quite different from your kimono looks."

I held my striker close, glaring at him.

"I didn't see the need to wear something else." I spun quickly as I felt someone coming at me and stopped them with my staff, cutting their torso.

"You shouldn't have come," Akaza snarled as he instantly regenerated his torso.

I turned to him and gave him a smile. "Oh but I really should. I'm here to challenge Muzan."

My son gripped his blade, his six eyes raging with emotions but like Doma, he did not say anything about it. "(y/n). You don't know what you're up against."

"Oh Michikatsu-"

He shot forward and unsheathed his sword, growling. "That isn't my name, woman."

"It's your birthname. If you really forgot your human side then you're truly lost." I shook my head with disappointment.

"I'm no longer human and neither are you, Mother." He spat out the word. "Should I even call you that? You abandoned us."

I gripped my staff tightly as he backed down, instantly striking his shoulder but I could not bring myself to follow through with harming him.

"I had no other choice-"

"There was always another choice." Michikatsu's blade clashed with my staff. "But I don't care."

"Clearly not." I put my leg over his sword and dragged him to the ground with the speed of my movements, pressing the blade to his neck. "Where is your bastard father?"

"You won't find him," Doma finally spoke up, pain clearly in his voice. "(y/n), stop this."

I gave him the look of pure hatred. "Don't tell me what to do, you liar."

I could tell Doma was sincerely sorry but I did not care.

I had a mission to complete and I knew I could not forget it.

Years ago, we had developed a relationship after falling in love but he betrayed me.

Ume and her brother were on the brink of death and even though I begged him not to, he turned them into demons.

And I would never forget it.

"Michikatsu. Tell me where your cowardly father is."

My son curled his lip. "Michikatsu is dead. I'm Kokushibo."

Instead of addressing him by his demon name, I mocked him by moving my hands in the form of a mouth as I spoke.

"MiChiKatsU is dEaD. I'M koKuShibo." I rolled my eyes. "Your name could be asparagus for all I care. To me, you will always be Michikatsu. Now I'll ask you again: where is your father."

"Why do you want to know?!" A female demon that reminded me of Ume spat.

I sighed and gripped my staff. "I wanted to do this the easy way. I suppose I should've expected you fools to delay my fight with Muzan. Yoriichi!"

As soon as I called, the infinity castle was torn open and my son came in, wielding his sword.

Thank you, swordsmen of the swordsmith village.

"Oh now the party's begun," the female demon smirked as she took a good look at my sons.

I looked at the female demon with curiosity. "You must be the new rank 6."

"Are you dumb?" Kokushibo snapped. "That's Ume. The one Doma turned into a demon."

My eyes widened as I realized this was true.

So this is little Ume...where is her brother?

Doma looked at me with sorrow as he trapped me in an ice technique.

"I'm sorry, (y/n). But you cannot-"

I quickly unleashed the power in my staff, glaring at him. "Starlight Breathing Second Form: Raging Star."

Purplish-red emerged from my sword as I cut Doma's head off, rage in my movements.

But instead of dying, Doma simply put his head back on, annoyance flashing in his eyes.

"Really?! We haven't seen each other in a few years and instead of hugging me like we did that night, you choose to slice off my head!"

I glared at him, not breaking my focus. "Shut up. Tell me where Muzan is."

"No! First you show up randomly after running away and disguising your scent so I can't track you. Second, you show up with one of your sons and are a wielder of a new art created by said son! Yoriichi-"

Yoriichi glared at Doma but did not move against him. "Keep my name out of your filthy mouth."

"Someday you will realize how powerless you are against us demons," Doma shook his head at my son with disappointment. "I'd expect you to realize that sooner or later."

"Oh will you just shut it?" Yoriichi and I attacked him at once only to be stopped by Muzan himself.

"My beloved wife and son," Muzan's shrill voice reached my ears and I instantly turned around, unleashing an attack on him.

"Starlight Breathing First Form: Striking Moon."

Muzan easily deflected it, smirking. "Like Mother like Son. (y/n), our dear Kokushibo shares a breathing for the moon. It is only fitting that you are the stars."

"Oh shut up!"

But before I could move, one of Muzan's demons moved the castle so only I was facing my husband (as we were still unfortunately married), my sons facing each other.

Muzan sat down as we were in a sort of living room setting, glaring at me. "Why is it that you choose to return now? And why did you turn into a demon? Why did you truly do it?"

I smiled as I raised my staff. "To kill you. There's a reason why I created the demon slayer corps, dear husband of mine."

Muzan and I clashed together, my face inches away from him. "You ungrateful bitch. I took your family out of debt and gave you two sons. They are going to rule-"

"But that's the issue!" I spat. "You turned our Michikatsu into a monster! All for the sake of having an heir to rule demon and humankind someday!"

"It was the only choice-"

"There is always another choice!" I lowered my guard for a slight moment only to grab a poison-laced dagger and stabbed it in his eye.

"You're a fucking hypocrite! You abandoned our children! And you have the nerve to lecture me on having another choice." Muzan quickly regenerated his eye, chopping my arm off.

I quickly regenerated my arm and jumped back, glaring at him with full hatred. "I did what was best, or I thought so."

"When you realize you can't delay the inevitable, you will truly see my plan," Muzan said as his voice got softer. "There's a reason why I chose you."

"Shut it! I don't want to hear any of your-"

Muzan suddenly was in front of me and he slammed me against the wall, holding my wrists with one hand, my striker dropping to the floor with a clang.

"Out of all my brides, only you have produced an heir that is both human and demon. That is the only reason why Yoriichi and Michikatsu-Kokushibo are able to use demon slaying techniques and awaken their demon marks."

"Oh cut the crap!" I quickly hooked my leg under his and moved quickly, slamming him to the ground. "I know you've had hundreds of wives! And your children-"

"All of which are human or demon," Muzan spat. "Akaza. He's one of my children. He was born a human and lived a life of pure hell. Daki and Gyutaro. Also born human. They are the only ones in the upper ranks that I deemed worthy to turn into demons."

I was taken aback by what he said. "So you're essentially saying most of the upper moons except Doma and that girl are your kin?"

"That would be correct. All failures-at first. The only reason why I let Doma turn you into a demon is the simple fact that I am the demon king and you-" he reached up and touched my face almost gently. "You are worthy to be my demon queen."

"Hold on...you only told me some of your human-turned-demon children. What about the others?"

"Failures with weak minds. After I killed their mothers, I let them lead lives of misery. Some of them made good food for my other demons."

"That is horrible!" I yanked his hand off me. "Ok so what if I believed you? Why did you let Doma and I-"

"I didn't. He's only a pawn, (y/n). I told him if he made you fall in love with him and conceive a demon child, I'd give him more of my blood. He doesn't love you."

"I already know he doesn't love me," I snapped. "He made that clear by turning Daki and Gyotaro demons."

"That was my order." Muzan shoved me off him, pacing around. "I abandoned them when they were children then not even a year's time after you found them in that disgusting village. I suspected that he would fall in love with you, (y/n). He'd be a fool not to."

"Huh?"

"Even though I didn't treat you right, I still love you." Muzan stepped back towards me, staring at me with fire in his eyes. "You will be by my side for eternity."

My eyes widened at the familiar words, striking chords of deep emotions within me.

Flashback, five years ago

"Doma!" I called out to my lover.

He quickly appeared with a towel, concern in his beautiful eyes. "Yes?"

I looked up at him and leaned against the side of the bathhouse pool, sighing. "Come in."

"With pleasure."

Doma slowly removed his clothing and slid into the warm steamy water, hugging me.

"Are you ok?" He asked me as he placed his head on my shoulder softly.

"Why?" I whispered. "After everything that's happened, why are you still here?"

"Silly girl. I love you. I've loved you since I saw you that night seven years ago." Doma turned me around and hugged me tightly. "We could be enemies and my feelings will not change. (y/n), I would tear the world into pieces. Just for you."

I felt his arms wrap tighter around me and sighed. "I see. Would you give your life for me?"

"A thousand times over."

I looked down at our reflection and sighed. "I love you."

I felt his heartbeat accelerate. "Really?"

"Really. You've shown me love that I never knew existed. Seeing you with the children and of course being by my side when Michikatsu and Yoriichi..." I felt searing pains in my heart as I recalled everything that had happened. "I love you, Doma."

Doma's hands touched my face and he closed the gap, kissing me for the very first time.

He broke it apart, staring at me with so many emotions swirling through his eyes. "I love you so much, (y/n). I really do."

"I love you too."

I felt him place his lips on my neck, giving me tingling sensations as he kissed me ever so gently.

"For our eternity. You will be by my side for all our eternity."

End of Flashback

"I'll never let you!" I shouted to him. "You have ruined any chances! Had you not abused me for those years, you might've had a chance!"

"Why should I?! Back then I wasn't sure if you'd be able to give me an heir that I desired."

"Oh cut the bullshit with the heir! Like hell Yoriichi or Kokushibo will replace you! You're too much of an egotistical maniac to allow someone to take your throne!" I focused on him and I could see into the transparent world.

What the-he has multiple hearts?! This won't be easy.

No One's POV

Just as (y/n) and Muzan were fighting, Yoriichi was confronting his twin.

"Our mother did it to protect us!" Yoriichi screamed as his blade clashed with his older twin's.

"Stop believing her lies! Only Father cares about us! She never-gah!"

Yoriichi had managed to cut his brother's back, spitting with deep sorrow. "You've been lied to. Father won't ever go away from his throne! Stop lying to yourself! You're nothing but his puppet!"

"SHUT UP! YOU KNOW NOTHING!"

The two brothers faced each other, sun and moon.

"I've moved on!" Yoriichi spat. "Stop crying because our mother did what was best! Think back to your own son! You left him to become a demon slayer-but became the thing you swore to never become!"

"IM NOT A WEAK HUMAN LIKE YOU." Kokushibo twisted his body and cut a hole through the air, Yoriichi barely being able to dodge it.

"THIS IS THE END, BROTHER! SAY A PRAYER!"