SAO: Uchiha Izuna Transmigrates

After Uchiha Izuna was killed by Senju Tobirama's Flying Thunder God Slash, his consciousness did not vanish completely. His fierce determination to "protect the Uchiha" and the Sharingan's special ocular powers caused his soul data to be captured by accident, and he transmigrated into the timeline of Sword Art Online. The transmigration mechanism can be explained as a quantum resonance with the principles behind the "Fluctlight" technology. When he awoke, he found himself in the Tokyo metropolitan area, back in the body of a five- or six-year-old child with no identity records. While wandering the streets, he was found and adopted by the Kirigaya couple, Kirito's adoptive parents, becoming Kirigaya Kazuto's younger sworn brother and receiving the name "Kirigaya Izuna."