Oroku Nagi was a formidable member of Japan's deadliest ninja clan the Foot. His only rival was a man named Hamato Yoshi with whom he competed in all things including to win the favor of the Lady Tang Shen. Unfortunately from the beginning she only loved Yoshi. Enraged Nagi went to her home and demanded that she love him and began to beat her, at that moment Yoshi walked in. Nagi was soon killed by a furious Yoshi.
By killing a member of his own clan Yoshi's shame was great and he was given the choice of ritual suicide or exile from the Foot. Yoshi chose the latter option taking Shen and his pet rat to start a new life in New York. In Japan however Nago younger brother Saki was brought into the Foot who used his anger at his brother's murder to mold him into their fiercest warrior. At a the age of eighteen he was chosen to go to America and lead the New York branch of the Foot. Now calling himself the Shredder, he too this opportunity to track down both Yoshi and Shen and murder the defenseless couple in cold blood.
Little known to Saki at the time, Yoshi's pet rat which would later be named Splinter escaped and along with four baby turtles was exposed to a substance which mutated them giving them human characteristics. Splinter trained the turtles in art of ninjitsu. Thirteen years late after the turtles had passed a test of beating a street gang known as the Purple Dragons Splinter told them the story of Yoshi and Nagi and told them that they must avenge his master by killing the Shredder. The turtles would challenge Shredder to a dual to a death in which they were victorious. Shredder how ever was resurrected and would menace the turtles again before finally being killed again and staying dead.
On a trip to Japan, Splinter took the turtles on tour of the remains of Yoshi's house and later in Shen's they encountered Nagi's ghost which battled the group as well as keeping two children hostage. A fire broke out burning down the house with Splinter, the turtles and the two children escaping. Splinter believed that final the spirit of Oroku Nagi had been removed forever.