Yu Yu Hakusho (1992)

S2E27 The Death of Genkai

Fifty years back, Genkai and Toguro were allies who triumphed in their own Dark Tournament, but their relationship soured violently over time. As Yusuke Urameshi rushed in, he witnessed the brutal death of his mentor, prompting him to attack Toguro in a fit of anger, only to be sent flying by a single, crushing blow. With the last round of the tournament looming against Toguro, Yusuke must devise a plan to prevent history from repeating itself.