Eternal Mangekyō Sharingan

The Mangekyō Sharingan's abilities drain a considerable amount of chakra when performed. Its usage and activity also place a great strain on the user themselves, wearing at the user's body and causing deterioration to their vision until eventually over-usage leaves them blind.[5] Their vision can be restored by receiving the transplanted Mangekyō of an Uchiha with strong blood ties — ideally a sibling — thus awakening so-called Eternal Mangekyō Sharingan (永遠の万華鏡写輪眼, Eien no Mangekyō Sharingan).[6] The Eternal Mangekyō merge the designs of the transplanter and the transplantee original Mangekyō. Their Mangekyō-based abilities are made stronger and they no longer suffer any negative side-effects from the usage. According to Madara, the Eternal Mangekyō Sharingan is proof an Uchiha continues to seek something despite experiencing great losses. Should the eyes evolve to this state, the user will retain all their previous techniques from their original eyes. In addition to the unique techniques, the "straight tomoe" (直巴, Choku Tomoe) form of Madara's and Sasuke's Eternal Mangekyō Sharingan grants them fluidity in their movements when fighting.

As with any dōjutsu, Mangekyō Sharingan can be transplanted into non-Uchiha, granting them all its abilities albeit with steeper chakra demands. Abilities of a Mangekyō Sharingan can also be programmed to activate under certain circumstances, either within the user's own eyes or in a target of the user's choosing; this programming remains even after death.