Genbu

Genbu(玄武, Lit. "Dark & Mysterious Warrior") is a member of The Four Sacred Beasts. Genbu is takes on the form of an enormous Black Tortoise while in his beastly state. Shortly before migration to Takamagahara with the other four sacred beasts, Genbu taught a fraction of his powers and martial arts knowledge to a human by the name of Jackie Chun, making him involuntarily become the forefather of The Kame Sennin-Ryu fighting style, and The Original Kame Sennin alltogether.

Trivia

 * Of the Four Sacred Beasts, the author claims that The Black Tortoise is his favorite creation out of it and The Vermillion Bird, Azure Dragon, and White Tiger.