you are right.
Interesting idea, aren' t seals Yin based, I say that because we saw monks being good with seals in this manga, and monks train their spirit...
True, the fire temple sages, you meant right?
I'm sorry but are you trolling? You know Hagoromo had a brother right? Hagromo=Uchiha and Senju, Hamura= Otsustsuki(Moon) and Huyga. That whole theory was debunked years ago lol.
I'm talking bout origins bro.. kaguya was the origin of byakugan, she got rinnesharingan after eating the chakra fruit. Maybe, she got the rinne-sharingan instead of just the rinnegan which is known as the 'wellspring of ninjutsu' because of a reaction between byakugan and rinnegan? Think about it, byakugan has a better penetrative vision than sharingan but rinnegan has shown zero penetrative vision prowess except it can see chakra, but has shown the ability to see invisible things. So sharingan might've got the ability to see invisible things on a lower level than rinnegan like obito saw the invisible chameleon jutsu of an iwagakure shinobi + penetrative ability from the byakugan but on a lower level, since sharingan is more of a derivation from it.
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Byakugan can see chakra and its colour, and in all directions, rinnegan can see chakra and invisible things but no colour recognition, sharingan sees chakra and it's colour but on a lower than byakugan. Also another sequence is byakugan sees the fate 'future in the long run', sharingan can see 'immediate future'(pre-cog) and rinnegan can't see any form of future since madara awakened his rinnegan when he was about to die, which means he had no certainty about his future = rinnegan sees despair since it has no forms of pre-cog. Sharingan is the all seeing eye along with byakugan and rinnegan, but with the exception that it sees 'spirit'(seeing the ninetails inside of naruto which is a spirit), byakugan sees 'abstract things' like hope and fate, hence why byakugan users are practical with delusions about thier lives, rinnegan sees 'invisible' substances not visible to conventional beings, because it's a 'god'
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and sees 'unprecedented possiblities' as it's shown in the form of mastering all the six nature releases by the the time he was ten, which is totally 'unprecedented' in the shinobi world.
Just a theory. But I think it's kinda possible.