The Yellow Monkey (abbreviated "Yemon" or "Iemon") are often described as the band you'd get if you mixed 70's British glam rock and enka (traditional Japanese ballads) together. They started their career as an indie band who primarily played out of a Shibuya rock club called La.mama in the late 80s, which was something of a home-base for the "Japa-Metal" movement that sort of forked off into glam rock. The first several years of their career were spent struggling to find an audience, constantly being misclassified by Japanese media as visual kei. Their third major label album "Jaguar Hard Pain" finally started gaining them that audience in 1994, and their popularity slowly took off from there.
After 1997's "SICKS" was released, they were one of the most popular rock bands in Japan. This is viewed by many as Yemon's best album, and is a very influential rock album in general. 1998's "Punch Drunkard" continued that upward momentum, resulting in a tour made up of 113 dates that lasted almost an entire year. Yemon was at the height of their popularity, so it was the best time to release a game that would take advantage of this. The singles for My Winding Road and So Young had been released not too long before this game, and both are featured in some way.