Students Tokitou Minoru and Kubota Makoto are members of the executive committee of the student council at their school, Araiso Private High School. Their duties are to ensure that the school is safe and the students behave themselves. Licensed to fight and intimidate when needed, the duo takes care of any and all of the problems of their high school, along with the other members of the committee. With rash tempers, flirting and violent behavior abounding, Tokitou and Kubota will help keep the peace at Araiso Private High School – or fight trying!
In the mystical world of Shangri-la, demons and humans live side by side, watched over by a parthenon of ancient Chinese gods. But when normally-civilized demons start to go berserk, the gods require the services of Genjou Sanzo - a Buddhist priest with a magical gun, an evil-banishing scripture and a take-no-prisoners attitude. Aided by the ancient monkey god Son Goku, the half-demon Sha Gojyo and the demon exterminator Cho Hakkai, he sets off on a treacherous journey westward, with armies of demons, dark mages and angry gods all standing in his way...
Ok, these two anime have nothing in common except one thing: they are both made by the mangaka Kazuya Minekura. So if you like his style in animation and characters you might want to watch both Saiyuki and Araiso.
While I agree with tetra's recommendation, there is more to it for me. The whole structure of the series are very much in common. The major difference is the setting they take place in.
The characters got a lot in common, the animation style matches, just as a lot of character traits. Both series have the same kind of feel/atmosphere.