This Susanoo, the Kamui Susanoo, was stolen by Lin Nan from Kakashi's Kamui Susanoo.
After Obito's death, he used his remaining Ten-Tails chakra to transmit it to Kakashi, thus giving Kakashi a temporary experience of Obito's Perfect Susanoo.
This was a rather far-fetched plot point in the original work.
After all, this method of directly gifting one's Susanoo to another felt like forcibly giving Kakashi a cheat code.
The key was that Kakashi, who would previously collapse from chakra exhaustion after using just a few Kamui, could now activate Susanoo, which required a massive amount of chakra, as if it were child's play.
Even Obito wouldn't stand a chance in that state.
However, the end result was that the Susanoo under the power of dual Kamui immediately displayed overwhelming suppressive power upon its appearance.
Lin Nan even suspected that if the experience of the dual Kamui Susanoo had lasted longer, it could have soloed not just the weakened Kaguya at the time, but even the original Kaguya with her endless supply of Infinite Tsukuyomi chakra.
This was not an exaggeration.
Kaguya Otsutsuki was, in the strictest sense, truly immortal. Her body could absorb any ninjutsu and regenerate at an astonishing speed, which was why she could only be sealed and not killed.
It was precisely because of this that Kaguya initially had the upper hand against Naruto and Sasuke.
However, this all began to reverse with the appearance of the dual Kamui Kakashi.
Kakashi could be considered the man who got Kaguya's "first blood." He first suppressed her with Susanoo, then directly severed an arm. How ruthless was that?
And because the dual Kamui Susanoo allowed for the unrestricted use of Kamui's spatial ninjutsu, Kakashi didn't actually sever Kaguya's arm with a Raikiri. Instead, he wrapped Kamui's power around the Raikiri, transferring Kaguya's damaged tissue to the Kamui dimension, creating the illusion of a severed limb.
In reality, it had nothing to do with ninjutsu and naturally couldn't be absorbed by Kaguya's body.
This was the terrifying power of dual Kamui.
Obito's eyes were truly a bug-level Sharingan, far surpassing Itachi's Tsukuyomi on the left and Amaterasu on the right. While those sounded terrifying, they didn't have many impressive feats to show for it.
Except for Tsukuyomi trapping Kakashi for three days and three nights.
Itachi's strength lay primarily in his exceptional combat intelligence. After all, becoming an ANBU and then an S-rank rogue ninja in his teens wasn't a joke.
Take Uchiha Madara, for example. The original author didn't provide any definitive explanation for the abilities of his two Mangekyo Sharingan, yet he relied on sheer power!
But Obito's Mangekyo abilities were simply phenomenal.
With both eyes combined, he was absolutely god-like.
Instantly, his Mangekyo could defeat someone's Eternal Mangekyo!
It was a pure mistake that Obito never ambushed Kakashi to retrieve his eyes.
Had he gotten them back sooner, the Fourth Shinobi World War would have been over before it began.
He would have rather watched Kakashi pay respects at his grave from behind the scenes, only to throw away the flowers and utter a final 'Ougi' after everyone left, rather than attacking Kakashi.
Perhaps this was love...
Lin Nan recalled reading a fanfiction in his original world where the protagonist transmigrated as Obito with dual Kamui from the start and proceeded to conquer the ninja world...
Look at how others transmigrate, and then look at himself...
Even at the absolute endgame, he was still worrying about chakra depletion.
It was only when the dual Kamui Susanoo displayed its immense power that Naruto and Sasuke might have suddenly realized that Kaguya lacked combat intelligence, relying solely on overwhelming strength.
It was like a little girl with an arsenal of weapons, randomly firing shots and shells, but unable to fully utilize the arsenal's true potential.
This was why many said that having Kaguya as the final boss was worse than having Uchiha Madara be the boss from start to finish.
After all, Uchiha Madara truly knew how to play the game!
If Lin Nan hadn't had his system to cheat, defeating Uchiha Madara wouldn't have been a simple task.
However, Lin Nan's current strength was undeniably inferior to when he fought Uchiha Madara.
As for Sasuke, he was akin to Lin Nan at that earlier stage, capable of using both the Sharingan and the Rinnegan.
The only drawback was that he didn't have the Truth-Seeking Balls, but Naruto did.
After using the dual Kamui Susanoo, Lin Nan felt a significant depletion of his chakra and sighed slightly.
The dual Kamui Susanoo consumed even more chakra than Uchiha Madara's Susanoo.
This might have been related to the inherent Kamui power of the Kamui Susanoo.
Later, Lin Nan felt a sense of regret, thinking he should have bargained with the Six Paths Sage, perhaps asking for an incomplete Senjutsu body, so he wouldn't have to worry about chakra depletion.
He stole Kaguya's skills but dared not use them!
What a waste!
However, since the Kamui Susanoo could be activated, defeating Naruto and Sasuke shouldn't be a major problem!
All problems would be solved. Perhaps he could emulate Sasuke and gather the power of the Tailed Beasts within himself, thus resolving the chakra depletion issue?
No sooner said than done!
Lin Nan immediately threw two Kamui Shuriken at Naruto's massive Kurama and Sasuke's Susanoo.
Kamui Shuriken could track their targets by following their spatial movements.
Therefore, even though Naruto and Sasuke had witnessed the power of Kamui Shuriken, dodging them was not an easy task.
However, this wouldn't trouble Naruto. He just needed to throw a Truth-Seeking Ball to neutralize the Kamui Shuriken, thus ensuring his and Sasuke's safety.
What a clever move!
Treating a Truth-Seeking Ball as a disposable item!
Lin Nan, however, ignored them and headed directly for the Chibaku Tensei that had previously imprisoned the eight Tailed Beasts.
Sasuke saw this and became anxious. This was clearly his plan!
So, Sasuke immediately unleashed Amenotejikara towards Lin Nan.
"Swish!"
Lin Nan's vision blurred, and the next moment he found himself in a different location, while Sasuke was already charging towards the eight Tailed Beasts.
Lin Nan was about to use Amenotejikara to swap positions with Sasuke, but then he suddenly changed his mind.
Looking at the blood moon in the sky, Lin Nan was taken aback. He suddenly realized that it didn't matter if Sasuke took the Tailed Beasts' power.
Right, I can cast the Infinite Tsukuyomi!
After all, the Infinite Tsukuyomi could continuously absorb chakra from those caught in the genjutsu, so he wouldn't have to worry about chakra depletion.
Wait, what was happening with the plot?
The Six Paths Sage shouldn't have been unaware of his abilities!
So why did he grant him the power of the Rinne Sharingan?
Was this old man playing a bigger game?