In the Infinite Tsukuyomi, Konohamaru Sarutobi was smiling with glee as he was declared the world's youngest Hokage. The first two things he did as Sixth Hokage was to declare the Sexy Jutsu to be an acquired jutsu to be learned in the Accademy and to have Naruto as his assistant. But he did have three good reasons why he wanted Naruto as an assisstant: one, he couldn't deal with all the paperwork by himself. And two, he wanted to make sure he became Hokage because he wanted to and not because he was related to his grandfather, the Third Hokage. The third reason? Because he wanted to personally pass the mantle to Naruto when he became Seventh Hokage and become HIS assistant. His teammates, Udon and Moegi were happy and practically hugging him. His sensei, Ebisu was bursting with tears. And as for Naruto? He frowned with jealousy, but then he smiled and gave him a thumbs up. Konohamaru returned the gesture and promised he would be by his side when they switch roles.
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In the real world, Konohamaru, along with all of Konohagakure and the rest of the world, he was cocooned and connected to the Shinju Tree. Yes, not even the young genin were spared from this fate. They too were to become White Zetsus and become loyal only to Kaguya-hime. Of course, that won't happen for years, so the boy had plenty of time to enjoy his dream until the time came.
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The first year, Konohamaru's clothes disintegrated. He would not need them come the transformation.
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The second year, Konohamaru's chakra slowly began to become drained from his body. Soon, the jutsu he learned from Naruto will be lost to him forever. Especially the Sexy Jutsus.
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As the years passed, Konohamaru's body started to show signs of being drained of his chakra: his skin was becoming tight around his skeleton, his eyes were sunk into their sockets and his hair had lost its color.
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The more his chakra was drained, the more his personality and defining features were drained as well. The cocoon slowly started to bond with him and press into him, becoming like a second skin.
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As Konohamaru's self became slowly drained, a voice rang out in his head. A female voice telling him he would grow up not to be a leader anymore, but a follower. A soldier under her command, but for a greater good. He, along with thousands of others like him would follow her into battle against the interlopers who would dare steal her chakra. Konohamaru had no idea what she was talking about, but at this point, he didn't care. He was a soldier after all. And soldiers obey orders.
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What was left of Konohamaru now was nothing but a dried up husk, deprived of everything that made him Konohamaru. Now the transformation can begin. His skin turned chalk white with jagged lines appearing on it, his hair grew short and spiky and turned from black to green and his eyes turned from black to sickly yellow.
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Finally, the cocoon began to peel away and White Zetsu dropped from the tree and onto the ground. There were thousands of White Zetsus just like him now. At the same time, there were humans who had not had the honor of being transformed, but now had all their memories re-written in order to worship Mistress Kaguya as the goddess she was.
White Zetsu had turned from a naive boy with foolish dreams to a proper soldier ready to protect the world, its people and its goddess. He smiled. It's better to be White Zetsu than Konohamaru Sarutobi.