Yu Yu Hakusho Vol. 4 (manga)

Training Day

The legendary exorcist Genkai is about to pass on her explosive demon-smiting techniques to one student--and only one. Trouble is, one of the people battling for the honor is a demon in disguise: the sadistic Rando, who'd just love to turn Genkai's power against innocent humans... unless Yusuke can defeat him! Then, Yusuke and Kuwabara must stop a quartet of demonic criminals from plotting a supremely sinister attack on the mortal world. At the gates of a labyrinthine fortress swarming with monsters, demons, and supernatural fugitives, these two teenage punks don't stand a chance in Hell--unless they can call for backup...