Wasn't it with special circumstances that Tenseigan was gained?
not really. The thing about the last arc of Naruto is that it's so messed up. Most of the revelations came as the story develops while the planned ones ending up being kept secret for the sake of not spoiling the movies.
As far as we know, Tenseigan came about later in Hamura's life. Whether or not it's a mutation is never revealed. It seemed to be just like Hagoromo's side of the family. Meaning that the Tenseigan is truly something that is natural rather than a special case.
I mean the whole ritual of the "Hyugas" had their eyes put into the Tenseigan Orb for the sake of not trying to get the Tenseigan. On top of that, the entire process is the same deal and that is to get the other parts from the other family (in Toneri's case, the reverse Madara where Toneri ending up stealing the eyes like Madara stole Hashirama's chunk of his body).
That is to say, that initially it is still Byakugan vs Rinnegan.
yeah since Yin Otsutsukis have the Rinnegan naturally while the Yang Otsutsuki have the RSM (whatever they could be).
Kinshiki and Kaguya didn't really reveal anything unqiue. Both of them were fodder. Just a TenTen or recap of Part 1 (bone and palm stuff).
Heck, we still didn't get any special techniques of the 3rd eye from Kaguya's/Madara's and Momoshiki. At best the special technique is Karma. As for the IT, it is basically a planetary side genjutsu. Just a massive powerup of a Sharingan tech. It isn't unique. I was expecting more. Taking in the God Tree, again, didn't really see anything about it. I mean she blew up into a rabbit? Big woop! Toneri did the same thing when he started absorbing the sun's power and he isn't even at 3rd eye level or even complete Tenseigan RSM level.
In terms of ocular, yes. The Yin Otsutsukis get the Rinnegan while the Yang gets whatever RSM they got. I don't think Kinshiki had any ocular techniques.
However, this still makes Tenseigan an unknown. Should the entire series have included the Tenseigan from the very beginning, would Kaguya have it or is it strictly a Hamura lineage thing? Does having the Gedo Mazou unlock his ocular powers? If so, how come Kaguya didn't get it when her body is the Gedo Mazou (well, people can argue that it is the God Tree but we know that the God Tree is the bloom of an Otsutsuki chakra fruit).
If youre worried about power levels not evening out (Rinne / Byakugan)
No, even if we do Rinne/Tensei, they shouldn't even out. Since the rule is that Yin = Yang. Having Rinnegan being the Yin, then Yang RSM is equal to it and not the Tenseigan. Making the Tenseigan equal to the Yin RSM.
Basically, Hagoromo = Hamura. Hagoromo being the ocular user while Hamura being the enhanced user. This proves true to the backstory of Hagoromo having Rinnegan and Hamura not having the Tenseigan.
This also proves true to the 2nd generation (Indra and Asura). Indra having the Mangekyu and Asura having the Avatar.
This isn't a local thing as well. This also proves true to the "Hyuga" and "Uzumaki" where one has the eyes and the other has the enhancement. (Toneri having CM and having to steal a Byakugan from a "royal" line).
But again, if we are only speaking on terms of ocular power scaling, clearly Rinne = Tensei and not Byakugan. If we add Ikemoto's contribution:
Rinnegan = Tenseigan
Mangekyu = Jougan
Sharigan = Byakugan
Basically, if Neji and Hinata could see over several kilometres, then aliens should be able to see over entire countries
I don't doubt this one bit since they are purebreds and isn't diluted with other traits that can weaken or take away the effectiveness of the Byakugan powers. I think this is even more expected otherwise that's BS to have the scaling be the same no matter how diluted your blood gets. Totally messes the whole point of "closer to the blood of the originator (3-eyed GT Kaguya), the similar the power is"
Doesn't the symbolism of the 6 paths speak against the likelihood of other aliens?
Well this is just a theory that the 6 people had their own unique powers (path). Even if they are unique powers, it still does not mean that they banded together out of their own desire. It is most likely a societal culture that they follow this system.
Remember Kinshiki's remark about his predecessor? Meaning that there WERE other people like them. So it is confirmed that it isn't just the 6 of them originally. Kinshiki had a predecessor means that there were other people comprising that 3 pairs team.
Whether or not that group is unique is another matter. Are there more ACTIVE 3 pair teams or is it only 1 at a time?
Is it by generation? Kinshiki seem to mentioned that there have been a moment where a pair had to transcend forcefully (which is probably a big deal and shouldn't be taken likely based on their reaction).
So 2 things:
1) there WERE other members
2) there could still be Otstusukis and have their own teams (not necessarily comprising of 6 but they most definitely be at the very least a pair)
Such that if others exist, they are not related to paths?
That still remains to be seen. I'm sure there are fodder Otsutskis who can't use any paths. But there are certainly other Otsutsukis out there based on Kinshiki's remark.
As for paths, I don't think because they are unique that it prohibits others to not be able to be one. They could just be based on affinity.
Unless you are implying something like a Jin where only 1 could be a Jin of a TB at a time. So like the Rinnegan(s) were implanted or inherited somehow and the same for the RSM. The rest of the Otsutskis were truly just fodders and there were 6 individuals that were chosen in their civilization to cultivate and harvest and guard for the Otsutsuki race.
That is also possible. But I think the former would be most likely. How there are other Otsutsukis that have their own power/path.
Even so, they are always explained within the story.
Sasuke, for example, got his 1 eye Rinne-Sha because he did not naturally awaken his eyes.
yeah exactly but that's no excuse for Boruto. His wasn't a forced awakening. He truly is capable of that since he is the older sibling (meaning that he will get the ocular power while Himawari will get the enhancement power). His mother is powered by Hamura and his father is buffed by Hagoromo.
So if we do the counter of Yin-Yang, the count would be:
1 Yin Hamura
1 Yang Hamura (this is assuming that the powerup that Hinata got is complete and that Toneri's clan IS NOT tied to the Uzumaki
1 Yang Hagoromo (seal power up/Uzumaki is Senju: RS reincarnator plot)
1 Namikaze clan
So he is 3/4 Otsutsuki (doesn't really matter which plotline you choose for the Uzumaki since Yin Hagoromo is the one missing). This is also true for Himawari BTW. It's just hers would be the enhancement one. She already have proven that it would be the case since she knocked out Naruto and Kurama using taijutsu (yes I know it's a comedy gag and she used Byakugan but it really is just to assist the attack and not being used as the actual attack)
For the last part, i think your Yin within Yang within Yin theory covers it quite well. Even if Kaguya was a Yin/Yang, her kids can/will have a duality of powers.
So scenario #2? The exchange of seals?