Board Thread:Naruto Discussions/@comment-36221354-20180717114536/@comment-34938099-20180805065844

In my opinion, you don't exactly need a Sharingan for awakening the Rinnegan. It's just that evolving Sharingan to Rinnegan is one of the many ways you an acquire the Rinnegan. As far as we know, you it is not  compulsory  that you need the Sharingan to get Rinnegan. Yes, you can get Rinnegan through Sharingan but it's not the  way  you can acquire. Because Otsutsuki like Momoshiki, Urashiki, Kaguya, etc. awakened THEIR ocular powers ( I.e Rinnegan, 6-Tomoe Rinnegan, Rinne-Sharingan ) by eating Chakra fruits from one of the God trees across the Universe / dimensions, most likely.