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The Rinne Sharingan (literally meaning: Saṃsāra Copy Wheel Eye) is a dōjutsu kekkei mōra and the predecessor to the Rinnegan and Sharingan (and by extension their in-between stage, the Mangekyou Sharingan).
It is characterised by red sclerae and irides, with a ripple pattern spreading over the eyeball and nine tomoe. In its sole known user, it acts as a third eye.
Note that Sasuke’s variant of the Rinnegan is often tagged using this tag, even though that’s technically incorrect.