Hakuryu (original name Jiipu) is the Sanzo party's transportation/mascot, a small white dragon with the magical ability to take the shape of a jeep. This gives him greater strength and carrying capacity, but is a very tiring form for him to maintain, and when ill or tired he cannot shapeshift at all. As both a dragon and a jeep he has the ability to fly, though he seldom flies in car form. He is intelligent, understands human speech and can communicate (in a limited way). He belongs to Hakkai, who is his usual driver in jeep form and treats his dragon form as a well-loved pet.
It is generally speculated that he is the reincarnation of the Dragon King Gojun.
Hakuryu is the Sanzo-ikkou's mode of transportation. Although his normal form is that of a small, winged, white dragon, he has the magical ability to take the shape of a jeep, and in that form has carried all four of the party many miles. ("Hakuryu", meaning just "white dragon", is a name given him for the anime series; in the manga he has never been called anything but Jeep (Jiipu).) In jeep form, despite having the shape and relative strength of a large machine, he is still a living thing: he does not require gas or other automotive maintenance, he is still capable of hearing speech and responding to it, and if his hood is opened internal organs are seen. Functioning in jeep form is very demanding for him, and when ill or tired he cannot shapeshift at all.
In shape he is somewhere between an Asian and a Western dragon (technically he is closest to being a Wyvern). He can fly and has the ability to breathe fire, though he uses this power only in grave need. In character he is generally mild-mannered and patient, but he is fiercely protective of the ikkou and will fight to help or defend them.
Hakuryu apparently belongs to Hakkai, though how this came to be has never been explained. When he is a jeep Hakkai is his usual driver, and when he is a dragon he typically rides on Hakkai's shoulder. They have an affectionate "master and pet" relationship: Hakuryu is often seen sleeping at the foot of Hakkai's bed, being fed tidbits from his plate in restaurants, and the like.
He is intelligent to some degree, understands what is said to him and can communicate in response (though he has only one sound in his vocabulary, "kyu", it is surprisingly expressive and versatile). Sanzo is the only one of the four who never speaks to him.
It is often speculated that, like the other four, he too is a reincatrnated denizen of the Heavens, in his case the Dragon King Gojun.