Sensei Wu is the younger son of the First Spinjitzu Master. In Wu's childhood, he and Garmadon were the best of friends. One day in his youth, Wu lost his father's katana during a spar, and Garmadon climbed over the wall to retrieve it. While outside, the Great Devourer bit Garmadon's hand, corrupting him with its venom. As a result of the growing evil within him, Garmadon became increasingly distant from his family, but he and Wu would remain civil with each other for some time. When Garmadon married Misako and fathered Lloyd, Wu was happy for his brother, but also somewhat melancholy, as he personally harbored some affection for Misako.