Nagi competed with Hamato Yoshi (the owner of Splinter, the Turtles' mentor) for the love of a woman named Tang Shen. Shen loved only Yoshi, and a feud erupted between Yoshi and Nagi, which led to Yoshi killing Nagi and fleeing from Japan to New York City with Shen. This led to Saki swearing revenge on Yoshi.
In the Tales Vol. 2 story "A Ghost Story", the Turtles visit Hamato Yoshi's house and find that it is being haunted by Nagi's spirit. Splinter exorcises Nagi by burning the house down.
Oroku Nagi has never made any appearances outside the Mirage comics; however in the 2003 TV series, a character named Yukio Mashimi is loosely based on him. In the 1987 TV series Oroku Saki did have a younger brother Kazuo Saki who was a policeman in Tokyo.