Saiyuki (最遊記, Saiyūki) is a manga series by Kazuya Minekura which was serialized in G-Fantasy from 1997 to 2002. The story is loosely based on the famous Chinese novel Journey to the West. Currently the manga has two sequels Saiyuki Reload (2002-2009), Saiyuki Reload Blast (2009-ongoing), a prequel Saiyuki Gaiden (1999-2002) and a mini arc now running at Zero Sum Ward, -- Saiyuki Ibun (2009-ongoing).
Saiyuki is the story of four anti-heroes: the monk Genjyo Sanzo (or just "Sanzo"), the monkey king Son Goku, the half-demon Sha Gojyo, and the man-turned-demon Cho Hakkai (formerly known as Cho Gonou). They have been dispatched by the Sanbutsushin (the Three Aspects of Buddha, who relay the orders of heaven) to travel 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 own tragic personal pasts. Meanwhile, the villains, two unlikely confidants, Gyokumen Koushu (Gyumaoh's concubine, a demon) and a mad scientist, Dr. Ni Jianyi (a human), continue their attempts to restore the long-dead king. These experiments, a forbidden mixture of science and magic, spawn the "Minus Wave", infecting all of the demons in Shangri-La with madness, shattering the fragile peace that once existed between humans and demons.