Uzumaki Nanami is here, Dattebane!

Chapter 1: A new mission, A new world

AN: I DO NOT OWN KIMETSU NO YAIBA AND NARUTO EXCEPT FOR MY OC!
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Nanami POV

"Don't you dare touch my Nii-Chan!" I shouted as I ran in front of my brother from an all-killing ash bone from the rabbit goddess and the first chakra wielder, Ōtsutsuki kaguya. We were transported to another of her dimension that has powerful gravity which nii-Chan and Sasuke are struggling to dodge another of her attack. I used my hiraishin kunai to switch places with Kakashi-Sensei as I stood in front of them along with our former enemy and now comrade, uchiha obito.

"Nanami no!"

"What are you doing!? Run now!"

STAB

"NANAMI!!!"

I clenched my jaw in pain as we were then transported another dimension. My knees dropped as I felt my skin cracked.

"You've got guts," I heard obito said as he too is in pain as his skin started to crack.

"Yeah, well... I'm not gonna let my Sensei or any of my teammates die... even if it means sacrificing myself." I said, I then feel Nii-Chan's hand on my back almost like trying to heal it but nothing worked.

Black Zetsu started to explain that healing me and obito is inevitable as he started to mock obito, which made me angry. Nii-Chan was about to retort but obito acknowledged it, I looked at him in empathy as the cracks in our skin started to spread. Sasuke was then infront of kaguya, Chidori in his hand. But kaguya dodge it.

He then activated his susanoo and went after kaguya but not without sparing a glance at me then he goes after her. Our skin began to fall apart even more as I glance at obito and Nii-Chan.

"After fighting you... I feel like I've woken up..." I heard obito said as I glance at him as he fell silent, I lift up my hand as it cracks and falls apart bit by bit.

"It was as if, when I looked at you i saw my past self and regretted the current me... but for some reason, it also made happy... when I was a kid... I'd imagine myself as the hokage so often... I think you both brought back that indescribable feeling of exhilaration and uncertainty...." he said.

"Imagining the village, comrades, and me as hokage... even after all that's happened just the thought of it seems to fill up the hole in my heart..." he added then chuckled.

"Is it because that I'm dying? I find myself rambling all of a sudden..." he said as tears went up into my eyes and fell down on my cheeks.

"A lot more suffering likely awaits you, Naruto... however just keep on forging ahead like always... without changing... you once told me that never going back on your word is you and your sister's ninja way... right?" He said as our bodies fell apart into ashes.

"Yeah..." we replied.

"Naruto... you better... become the hokage!" He said his final words as fell into ashes.

"Nii-chan... no matter what happens... even if we're far apart from each other... we'll always be together... please... don't blame yourself... I made a choice... so that... I'll be the one saving you... this time, dattebane...." I said as I look at him with tears on my eyes and smiled, I noticed he was beginning to tear up.

"Nami-nee-Chan..." he said, memories from our childhood flooded into my mind as I then hugged him.

"Nii-Chan... don't be sad... I'll be with kaa-chan soon... and tou-Chan too... take care of yourself and everyone else... and fulfill our dreams..." I said before I crumbled into ashes.