Even though he was trained to abandon his emotions, Shin grew close to a younger Root member, Sai. He recognised Sai's talent for art, and encouraged him to continue the hobby. Sai looked up to him as a brother and began to shed Root's teachings, but Shin soon died of an unknown disease, leaving Sai's training to suppress most of his memories of Shin. Prior to Shin's death, it was noted that he and Sai were supposed to fight to the death by Root regulations, in a final step to eradicate emotions. After Sai met Naruto Uzumaki, who he noted to be similar to Shin, Sai's memories of him returned, which brought a smile to his face.
In the anime, where his story is expanded, Sai and Shin were forced to fight to the death by Danzō Shimura to fully kill their emotions. Knowing that he was terminally ill, Shin told Sai to report to Danzō that he killed him in battle. Before telling him to go, Shin told Sai that he must suppress his feelings otherwise, the missions undertaken by Root would consume him. As Sai leaves to report to Danzō, Shin dies.
Shin had grey hair and light-coloured eyes, which are depicted as black in the anime. When he was a child, he wore a pale yellow shirt together with a pair of dark brown pants. These outfits were the ones he wore in the cover of Sai's picture book. When he was older, he wore the official uniform of the ANBU, and carried giant shuriken as well as a tantō on his back. After being reincarnated by Kabuto Yakushi, it was revealed that at some point before his death he used to wear an outfit exactly like the one his brother wears inclusive of the customary Root jacket. In the manga, he also wore a forehead protector when he was reincarnated.
According to Sai, Shin and Naruto are very similar stating that Shin was also loud, impatient, and unrefined. Shin was also a very kind individual with a pleasant disposition as he helped Sai pursue his interest in drawing. He was also stated to be very tenacious and absent-minded.
Shin was a skilled shinobi during his lifetime, enough to be reincarnated by Kabuto to fight in the Fourth Shinobi World War. When he fought against the Alliance's Surprise Attack Division, he used a tantō similar to Sai's and was very skilled at close range combat.
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