Straight Tomoe Mangeky Sharingan is linked to Indra, since Madara (correctly) surmised that he and Sasuke had some relationship beyond blood owing to both of them waking Straight Tomoe Mangeky Sharingan, even if he couldn't determine their particular connection. It is also implied that being Straight Tomoe does not correlate to Mangeky Sharingan design, and that it also exists in the Sharingan stage: Madara's original Mangeky Sharingan did not have a straight design, but Izuna's did, and Madara stated that only he and Sasuke awakened a "Straight Tomoe Sharingan" rather than "Straight Tomoe Mangeky Sharingan." [33]
The last factor is what I would describe as "an overwhelming degree of Love combined with a deep guilty conscience." Itachi murdered out his whole clan in order to safeguard Konoha from the coup plotted by the Uchiha, but he couldn't kill his brother since he loved him more than anything else. Itachi was well aware of the gravity of his actions and resolved to make apologies by dying at the hands of his younger brother, who would attempt to revenge the whole clan. Itachi most likely reasoned that if he possessed the Eternal Mangekyou, Sasuke would have had no chance against him, and therefore resolved to confront his younger brother later on when his eyes had deteriorated in such a way that they would be close in power and not a one-sided combat. So that was all because to Sasuke! He knew he was dying and opted to die in the hands of his brother. By doing so, he utilized his death to strengthen Sasuke. Itachi planned to give Sasuke the upper hand in order to make the battle more equitable (by fighting him while he was partially blind and sick).
Uchiha, Madara
Madara and his younger brother Izuna were the first Uchiha to activate the Mangeky Sharingan.
[24] He finally became blind from overusing it, and it was only by extracting his younger brother's eyeballs that he was able to restore his sight. [25] [26] This also awarded him an Eternal Mangeky Sharingan, granting him even more strength. [27] His Eternal Mangeky Sharingan resembles his original, overlapping Izuna's.
Susanoo is regarded as the Mangekyo Sharingan's greatest ability, and it is only available to those who have awakened it in both eyes. Unlike the other abilities, this isn't limited to a single person. Instead, every Mangekyo Sharingan user has the ability to wield this power as the ultimate form of offense or defense. It enables the user to summon a massive chakra humanoid to battle and defend them. Its full-body shape is strong enough to cut through mountains with a single slash.
