Saiyuki is a manga by Kazuya Minekura based on a famous Chinese novel entitled Journey to the West (Xi Yóu Jì). I don't know how much of the novel is identical with the manga and the anime but for sure it looks like a new adventure.
Saiyuki starts of with Genjo Sanzo talking to the three aspects of Buddha. The god then dispatches Sanzo along with Goku, Gojyo, and Hakkai to investigate why the demon population who used to co-exist with humans were suddenly going insane and killing people. So the four warriors journey West to get to the bottom of the strange phenomenon. Anyway, I'm not gonna go into full detail of the plot 'coz I found this great manga review site that can do all that better than I can.
All that I can say is that Saiyuki (both the manga and anime) is definitely worth your time and money. The characters are interesting and the art is great.
Here's a bit about the characters that might interest you: (1) Genjo Sanzo: A smoking, drinking, gun-toting monk leading the group. Incidentally, he's the only human in the group. (2) Son Goku: Yep, this is where Toriyama got his idea for Dragon Ball. In Saiyuki, Goku is the god of monkeys (I think he's unaware that he's a god) who's about 13 years old. He likes Sanzo-sama but he'll ditch him for food. (3) Cho-Hakkai: Legend has it that when you bathe in the blood of a hundred yukais (demons) you'll become a yukai yourself. Hakkai became a demon when he killed a clan of demons who raped his beloved. (4) Sha Gojyo: He's a half-yukai, half-human outcast with a big attitude but a huge heart.
By the way, the manga and anime don't have the same story. The manga's focus is on the Kame-Sama arc, while the anime goes straight to the plot where Sanzo's group goes against the group of the war god Homura. Both arcs have the same great art and action-packed stories that will appeal to both mature readers and kids alike, mature readers will love the philosophical undertones in this title while the kiddies won't be disappointed with the action.
Saiyuki has been licensed by Tokyopop but you can search for a scanlation torrent in Google. Note that the scanlation torrent is only up to volume 9, so get ready to be left hanging in the air if you are into scanlations.
