Saiyuki is the story of four reluctant - and irreverent - anti-heroes: the monk Genjo Sanzo (or "Sanzo), the monkey Demon Son Goku,the half-demon Sha Gojyo (Water Spirit), and the man turned Demon Cho Hakkai (Cho Gono), dispatched by the Sanbutsushin (the Three Aspects of Buddha, who relay the orders of heaven) to India to stop the possible resurrection of the Bull-Demon-King, Gyumaoh. Along the way they are beset by inept assassins, bad weather, and their tragic personal pasts. Meanwhile, the villains, two unlikely confidants, Gyokumen Koushou (Gyumaoh's concubine, a demon) and a mad scientist, Dr. Ni Jenyi (a human), continue their attempts to restore the long-dead king. These experiements, a forbidden mixture of science and magic, spawn the "Minus Wave", infecting all Demons in Shangri-La with madness, shattering the fragile peace that once existed between human and Demon.
Sanzo-Ikkou
Genjo Sanzo (玄奘三蔵, Genjo Sanzō)
Sanzo is one of the four protagonists in the manga and anime series Saiyuki. His name is spelled Genjo Sanzo in the English anime and the Singapore English manga, while in the North American English manga it is Genjyo Sanzou (the -jō is spelt in hiragana as ji-(yo)-u, with a small yo to indicate a glide rather than separate syllables). He was rescued as a baby from the waters of the Yangtze river by Kōmyō-Sanzō. The boy was named Kōryū of the "river flow"; a name he used until he was thirteen.
He is generally called "Sanzo" by his traveling companions, although his full title is "The 31st of China, Genjo Sanzo". A brutal, worldly man, he doesn't fit the stereotypical image of the passive, or pacifist, cleric. Disregarding basic Buddhist principles, he smokes like a chimney, drinks like a fish, gambles, swears like a sailor, and generally follows his own path. Sanzo is a cold, rational thinker and somewhat aloof. When there's a job to be done he usually has Goku, Gojyo, and Hakkai do it for him. He is called an old man by Gojyo because he likes to drink tea while reading his paper, adn because he like to go to bed early. Arrogant and short tempered, he nonetheless prefers to remain above the melee unless the situation is desperate. He is strongly opinionated, and despite his terse demeanor, highly moralistic and quick to defend the weak. His primary weapon is a five-shot Smith and Wesson revolver, which he wields as an expert marksman and is rarely without in combat. A secondary "weapon" is the holy sutra he carries on his shoulders, the Maten Sutra ("scripture of darkness"). Last but not least, he's often quick to whip out his harisen (paper fan) and whack his way through the occasional intraparty conflict (usually Goku)
Son Goku
The brave, cheerful Monkey King of legend; an unholy child born from the rocks where the aura of the Earth was gathered. His brain is full of thoughts about food and games. To pay for the crimes he committed when he was young, he was imprisoned in the rocks for five hundred years without aging. He has no memory of what happened to him five hundred years ago. His original form, known as "Seiten Taisei" (or "Great Sage, Equal to Heaven"), is revealed when his golden diadem is removed or broken. While in his original form, Goku is perhaps the most formidable of the party, but also completely lacks reason, self-control, and the ability to discern friend from foe. Hakkai, without his limiters, was only able to restrain him long enough to put his golden diadem back on his head. Because of his optimistic personality, he's become the mascot character of the group; this 18-year-old of superior health is made fun of by Goyjo, yelled at by Sanzo and watched over by Hakkai. He's 162 tall (approx. 5'4"). His main weapon is the Nyoi-Boi, a magical cudgel that can extend into a sansekkon staff.
Goku has no memory of what happened to him five hundred years ago, and he doesn't remember that Kanzeon Bosatsu's nephew, Konzen Douji, reincarnated as Genjo Sanzo, acted as his guardian. 
Cho Hakkai (豬八戒, Hakkai Cho)
Cho Hakkai is the mild, polite and level-headed member of the group who always looks out for their day to day wellbeing. He takes on the more feminine roles: cooking, cleaning up after everyone, making sure their supplies are in order, and solving (or at least calming down) the arguments and yelling matches that happen frequently. He is also their healer, his kikou jutsu (chi manipulation/Qigong) coming in handy in battle in the form of ki blasts and protective barriers. He also owns a pet dragon, Hakuryuu.
He was formerly known as Cho Gonou. Though originally human, Hakkai became a yokai (and had his name changed) after he slaughtered the yōkai of the Hyakugenmaoh tribe (According to Japanese legend, a human can become a yōkai after bathing in the blood of a thousand yōkai) for the kidnap and rape of his beloved sister and lover, Kanan. Not much is known about his past, except that he was orphaned at a young age. He is polite and soft-spoken with a deceptively innocent demeanor. Gojyo and Goku get chills when they see Hakkai "angry" because they know how ruthless he can be. He is often the straight and responsible man of the group, known for his dry observations and aphorisms in the heat of combat. Hakkai’s primary weapon is his ki, a type of metaphysical energy, which in his case can also be used to heal injuries. He wears a monocle over his (artificial) right eye, the remnant of a self-inflicted injury sustained shortly after his dealings with Hyakugenmoah's tribe. His yokai limiter takes the form of ear bands on his left ear. Whe the limiters are removed he becomes a feared fighter capapble of competeing with Goku in his released state. Unilke Goku though he is able to keep control of himself for a period of time. When he first used this for to kill a large monster Goku feared him and wished to never make him angry due to the ferocity of Hakkai's full power. 
Sha Gojyo (沙悟浄)
He is the hanyou (half-yōkai) companion of the Sanzo-ikkō ("Sanzo's party"), armed with a shakujō (which is the incorrect name given for a yuèyáchǎn). Its crescent blade is attached to a chain and he can control it for a mortally-accurate long-distance attack.
His blood-red hair and eyes express his status as a half-blood, and he's often labeled taboo and unclean in general society. Part kappa (a water imp) and wholly a ladies' man, he can be friendly and easy-going until someone or something offends his innate sense of justice. As he was an abused child, he's quick to defend and fight for lost or wayward children, often without concern for his own well-being. He is the only person who smokes and drinks more than Sanzo and is almost always seen with a cigarette hanging from his lips. If Sanzo smokes like one chimney, Gojyo smokes like three. He fights constantly with Goku, and never passes up a chance to woo the ladies. And in the beginning of the story it is explained that Gojyo is looking for someone in particular. Out of everyone in the group, he is closest to Hakkai. This is probably due to the fact that he and Hakkai's former selves were very good friends in Heaven.
