Born in the Hidden Grass Village, Shiro Karasu was raised and trained by one of the most respected people in the village, Akai Senkou. Akai Senkou once told Shiro the story of a man from the Hidden Leaf Village whom he aided in battle during the great war between Hidden Leaf Village and Hidden Rock Village. This man, he later found out, became the Yondaime Hokage. In appreciation of his help in the war, Yondaime taught Akai one his his prized jutsu, Shunshin no Jutsu, and supplied him with 25 Thunder Kunai, which were used to perform the jutsu. This jutsu was later perfected without the use of Markings (Thunder Kunai), though by that time, Akai had already lost 22 of the Thunder Kunai. Though they weren't needed, Akai kept the 3 Thunder Kunai he had as his prized possesions. Under Akai's training, Shiro advanced through the ranks, from Academy Student, to Genin when he was 8 years old. At the age of 11, Shiro's team was accepted into the Chuunin exams. Shiro passed the Writing exam with 7/10 questions correct, and flew through the Forest of Death with the time of 42 minutes and 12 seconds. Finally, he made it to the preliminary rounds of the final part of the exams. He was pitted against a Leaf Village member, and won, while breaking his left arm ion the process. Before his final match, Akai gave Shiro all three of his beloved Thunder Kunai to use, since he could not perform the hand seals to properly use Shunshin no jutsu. In the final round, Shiro was to fight his own Squad member, Raiken Maguma. As soon as the match started, Shiro threw 2 of the thunder Kunai, one into the ground Raiken's legs, and the other hit his fore-arm. Raiken looked shocked and in pain, and all of the sudden Shiro was kneeling behind Raiken, with the other Thunder Kunai out and both of his legs slashed. Raiken fell to the ground in pain and Shiro was standing over him with the Thunder Kunai against his neck. The match was declared over and Shiro had become a Chuunin.  3 years later, Shiro became a Jounin at the age of 14. Arriving at Akai's home, he discover his beloved trained dead, on the floor. Next to him was a headband, seemingly the only thing leading to who his attackers were. The headband bore the sign of the Hidden Mist Village. Akai had torn it off trying to protect himself. Shiro had vowed to find out who had attacked and killed his trainer, and avenge his death. 3 years later, he became an ANBU, and since then, he has carried out missions and countlessly visited Akai's grave.