Fukuyama Masaharu’s “Rainbow” (“Niji (虹)”) was released in Japan in 2003. The said song was a hit and took the number one position on the Oricon chart for five consecutive weeks.
BEAST’s version of “Rainbow” will also be included in Masaharu’s “THE BEST BANG!! -ASIA LIMITED BANG!!-” to be released on April 6th.
Check out their Korean remake of the song.