They were 2 cloud ninja (Im fairly certain they were cloud ninja at least) who fought against the nine tails. The nine tails swallowed them and they survived by eating the meat/chakra from within the nine tails. They were soon crapped out. They returned with parts of the nine tails chakra embedded in them. In the manga, there is an epic battle between them and Darui, and one of them gets sucked into the gourd (the weapons the have are a few of the legendary weapons from the SO6P), and the other goes into a Stage 2 transformation due to the rage (like Naruto did against Pain). Im rather upset the game didnt follow this part very well, even though these two characters are kinda filler.
If you want to know more, read the manga (chapters 526-530) or watch the anime (episodes 268-269/270, I forget when the fight ends in the anime but its only a few episodes).