|(うちはさんじ, Uchiha Sanji)|
|Academy Grad. Age||5|
|Chunin Prom. Age||11|
Sanji, like her brother, was among the first generation of Uchiha born into the revived Uchiha Clan within Yamagakure just prior to the Fourth Shinobi World War. Sometime during the Samurai–Shinobi Civil War, Sanji was assigned to the "Expeditionary Force" (派遣軍, Hakengun), of which her brother was squad leader, with the mission of hunting down and slaughtering any remaining samurai still within the Land of Mountains. The early missions, however, proved unsuccessful when pitted against the samurai rebels flawless guerrilla warfare. Nevertheless, Ryun Uchiha—the current and First Yamakage—continued to send the force out to continue the exterminations. During these missions, Saburō and Sanji became much closer. The two became notorious partners who eventually began to shift the tide of Yamagakure's losses into victories on the battlefront.
These victories caught the attention of the Four Devas—the last remnants of samurai leadership in the Land of Mountains—who personally put together an ambush to deal with the Uchiha and their comrades. While on route to Yamagakure to report their most recent string of successes, the Devas executed their plans; easily killing three of the five-man team almost immediately. Despite their prowess with the Sharingan, the Uchiha duo was unable to fight off the Kage-level samurai, and, while trying to protect Saburō from what was to be a killing blow, Sanji was fatally injured and died shortly thereafter.
Sanji was visibly similar to her elder brother, possessing short, raven black hair, though she allowed her bangs to hang down on either side of her face, as well as large onyx-colored eyes. During the Samurai–Shinobi Civil War, she wore a form-fitting black suit which revealed her shoulders and a small portion of her upper chest. She was also noticeably shorter than Saburō, despite being close to his age.
Though much of her abilities are unknown, it can be inferred by her age upon promotion to Chūnin, that she was a talented member of the Uchiha Clan.
Sanji was particularly talented with transforming natures, being able to wield two—fire and lightning—a trait that proves difficult for even most Jōnin. Her skill with both is relatively unknown, however, it was shown in several of Saburō's flashbacks that she could preform a strange type of lightning-nature technique which involved charging her body with electricity.
The tragic loss of his closest friend and sister awakened Saburō's Mangekyō Sharingan and Kamui ability simultaneously. With Kamui, though using it unconsciously, Saburō was able to reverse the tide of the battle which killed Sanji, forcing the Four Deva to retreat.
- When written as 惨事, Sanji's name translates to "horrible accident". This likely refers to the manner of her death.
- Sanji is one of the few known Uchiha to have not awakened their Sharingan.