Shin Uchiha is the main antagonist of the Naruto Gaiden arc in the Boruto Anime. He’s a powerful foe who was created by Orochimaru, as an experiment. However, he fell out with him and soon left his company. Along the way, shin found out about the Uchiha clan, and began calling himself an Uchiha as well. What’s more, he was so deeply inspired by Itachi Uchiha that he wanted to avenge his death.
Shin went to great lengths to achieve this. From attacking Sasuke directly, to trying to capture his daughter, Sarada Uchiha.
Shin is a pragmatic, scientific individual who adheres strongly to the evolutionary principles of survival of the fittest and natural selection, believing that living organisms are slaves to their genes and exist only to survive by passing on their strongest traits to the next generation. As such, he sees conflict as a necessary component of mankind’s evolution and seeks to revive Akatsuki and bring an end to the peace of the world, which he believes will cause the human species to stagnate and ultimately become extinct.
His powers were enough to surprise Sasuke, but not enough to beat him. Shin possessed tremendous amount of chakra, and along with that, the Kekkei Genkai of the Uchiha Clan as well. Shin had access to the Sharingan, thanks to Orochimaru.
He had awakened the Sharingan in both his eyes, and further, just like Danzo, he had them embedded all over his body as well. But, the most shocking ability that Shin Uchiha possessed was the Mangekyo Sharingan itself.
We all know that Mangekyo Sharingan is an ability that can only be awakened via the death of someone close to the person.
So how did Shin Uchiha awaken the Mangekyo Sharingan?
Let’s see the meaning of the sharingan first.
A Mangekyō Sharingan is distinguished from a normal Sharingan by its appearance, which changes the form of the tomoe seal. The exact design differs for each user, though all resemble pinwheels. It is initially awakened by the trauma suffered from witnessing the death of someone close to the user. Uchiha have historically misunderstood this criteria as the user needing to be responsible for the person’s death, and for that reason they developed the practice of killing their closest friends in order to gain the Mangekyō Sharingan. Obito’s Mangekyō activated immediately after his trauma, whereas, in Naruto Jinraiden, Sasuke’s Mangekyō didn’t activate until several weeks afterwards.
The Mangekyō Sharingan retains all of the Sharingan’s generic abilities, such as casting genjutsu and the ability to distinguish chakra. In addition to these, the Mangekyō grants powerful abilities that differ from user to user, though abilities may be similar in nature; both Sasuke and Itachi have access to Amaterasu’s flames, though the extent to which they can use them differ. The abilities of a Mangekyō Sharingan may not even be the same for both of a single user’s eyes, as Itachi has Amaterasu in one eye and Tsukuyomi in another. Once a user awakens the Mangekyō in both eyes, or the ability of both of their eyes, they are able to perform Susanoo. In addition to the unique techniques, the straight tomoe of Madara’s and Sasuke’s Mangekyō Sharingan grants them fluidity in their movements when fighting. Madara was able to sense this form and later deduced that he and Sasuke must be connected by more than blood.
I believe Shin awakened the Mangekyo Sharingan due to Itachi’s death. He was deeply inspired by Itachi when he found out about him. When Shin found out that Itachi was killed by Sasuke, his Sharingan evolved into a Mangekyo Sharingan.
I know he wasn’t there to witness the death. However, that is not necessary. If a puts you into deep shock, it is enough to help awaken the Mangekyo Sharingan.
Shin soon sought revenge on Sasuke Uchiha and even though he tricked both Naruto and Sasuke a couple of times, he couldn’t really pose a threat to either of them. Shin also used his Mangekyo Sharingan ability against them.
His eyes have the power to telekinetically manipulate weapons that he has branded with his special mark. Once he does that, he can manipulate any weapon.
He was even able to stab Naruto. However, he recovered soon enough. Shin’s Mangekyo Sharingan was troublesome to begin with. Even his clones have the same Mangekyo Sharingan ability as him and they’re all extremely powerful as well. Shin Uchiha could also use a Space-time Ninjutsu, but it is unlikely that he could use it via his Mangekyo Sharingan.