'hmmm, 57% purity level. Lived for 3 cycles as a human. And it seems this soul has acquired just enough experience, to be sent onto the trial. Okay system, proceed to inject the new model. And send this recording to head office.'
[All commands have been completed Agent K, enjoy your well-earned vacation.]
'Thank you, System. I've managed to book a particularly great universe this time. I will be able to say my favourite line: It's Morphin Time!'
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'wah! oh! I died.'
{That is correct, host. Please wait a moment, whilst system fusion occurs}
'How strange that every possible thought, idea and memory is completely passed without a measure of time.'
{You should now receive all information that you have the authority to access. When ready, please start the selection process.}
'I select the Naruto Universe, transmigrated into Itachi Uchiha and with Sage affinity.'
{Thank you. Please standby, as your soul is fused into the new physical container.}
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'hmm, interesting. Now that I have a body and most importantly a brain, my ease of understanding has been vastly diluted and reduced due to the sheer energy and work needed to operate the entire body via the brain. At least I can intuitively feel a part of my soul operating everything. I can only theories that my consciousness is so strong, due to my past lives.'
(The main point)
New transmigrator/Itachi uses common sense, hard work and also sage affinity to become the strongest.
Use nature chakra to strengthen and heal the body, and slowly evolve eyes to eternal without killing or swapping eyes.
Itachi will become a true ninja.
Most important, is to create realism in the world, fights, training and capability.
This will most likely be a long term naruto story.
Could be broadened into other universes but not until Naruto story is complete.