Pu (ぷう, Pū), or Pusuke (ぷう助, Pūsuke), known as Puu in the English anime, is Yusuke's spirit beast.
Puu is a small, beady-eyed, bird-like creature with an all blue body, white belly, a yellow beak and feet and a small patch of black hair on his head; which mimics Yusuke's hairstyle. His ears are big and floppy, but long enough to be used to fly. After Yusuke's revival, Puu takes on a larger appearance, transforming into a bird with a long neck, large wingspan, long elongated ears, a long black mane and large tail-feathers. In this form, Puu becomes large enough to be ridden by four people.
Puu, being a spirit beast, mimics the personality of its master. However, in contrast to Yusuke's slacker, bad-boy attitude, Puu is actually very sweet. He helps Yusuke get through his spirit orb training, as well as leads Keiko to find Yusuke should he ever be in trouble.
Spirit Detective SagaEdit
Yusuke received his egg early and was told by Koenma that a spirit beast would feed off its owner's energy and take its form based on the nature of the energy. In other words, if Yusuke is good, the creature inside it would reflect Yusuke. If Yusuke is evil, the negative energy would turn the creature inside the egg evil. And when it would hatch, the beast would eat Yusuke, leaving nothing, not even a spirit. Having sacrificed his first egg to save Keiko from dying in a fire, he was given a second egg.
Dark Tournament SagaEdit
The egg did eventually hatch though, and proved to be good. Although he hated Pu first, Yusuke grew to love the little beast after he worked so hard to get Yusuke a drink of water when he was undergoing Genkai's spirit wave orb test. Yusuke normally leaves the task of watching Puu to Genkai or Keiko, who both enjoy the job.
Chapter Black SagaEdit
While fighting Shinobu Sensui, Yusuke's ancestor, Raizen, took over his body. His demon genes awakened, Puu evolved into a more realistic-bird with wings and grew powerful enough to withstand the attacks of the Spirit Defense Force, each member ranging from Mid A class to Upper A class while protecting Yusuke, Strongly implying that Pu reached Upper A class since he is Yusuke's Spiritual Beast. Puu is Yusuke's ride to the Demon World for the final confrontation against Sensui. His appearance didn't change, though, even when Yusuke overcame Raizen's control. Genkai took him back to live with her, where he stays in her back yard. Strangely enough, Puu takes the form of Yusuke's spirit energy, a phoenix, as seen in the final round of the Dark Tournament.
Near the conclusion of the manga, Genkai possesses Pu as she did during Yusuke's fight with Toguro after her death. She gives words of confidence to Yusuke, who attempts to disarm a weapon capable of destroying the Earth which has been set in place by a cult who has taken Spirit World's residents hostage. Genkai then tells Yusuke to press which button he feels like, hoping the one he presses will disarm the weapon.