Board Thread:Theories and Speculation/@comment-35023081-20190918151946/@comment-38812954-20190919115634

Power always has a source and a mode of expressing itself. After eating the chakra fruit kaguya got a rinnesharingan. Applying the same concepts large chakra (and senjutsu) + sublime mental energy. The chakra fruit simultaneously grants you both of these. So momoshiki having rinnegan as I think is because that. He received rinnegan unique to him. Both in form (what kind he got) and fashion (where he got them. Particularly on his body) All chakra is/was a product of nature energy, and to receive power from the source of course will grant you anything out of what you can imagine.

Continually, large chakra and senjutsu or sublime physical vitally is yang power. Mental energy (the mangekyou in this particular case) - yin power. In the case of asura and indra's reincarnates, both of these combine, or have to combine to stimulate the rinnegan. Hagoromo's mangekyou went straight to the rinnegan because he simultaneously possessed both of these powers. Obviously having large chakra first because of kaguya and then getting senjutsu later. Then awakening the mangekyou, which reacted to these certain stimuli or conditions then evolved to the rinnegan (I for one greatly believe that senjutsu is the ultimate stimulus here). To possess both rinnegan you have to have both of these powers, clearly shown in the case of sasuke. Momoshiki having rinnegan in unorthodox sections of his body, like with danzo applies the same concept. The chakra fruit (to say again) instantaneously granted him both of these powers giving him rinnegan in a fashion unique to him (like how it was unique to kaguya) in various sections of his body. (like again danzo. Who had to take one of the powers to possess the other power). I hope you understand.

The Otsutsuki (most. apart from jigen) are originally Byakugan users. The boruto series will most likely portray to us the history of the Otsutsuki clan and their story. They've already shown us a little bit of what they do.