It's A Battle Royale, Capcom® Style!
The arcade-style 3-D fighters Power Stone® 1 & 2 come together in one great collection with brand new features and enhancements exclusive to the PSP® (PlayStation®Portable) system.
Source: The Developer Website.
From the Game Manual / Box
Take back the power!
You are just a roundhouse, back flip, spin kick away from victory with this great new collection of two classic games. Fight with twice the power and heart of stone.
Challenge you friends:
Two players in Power Stone and up to four players in Power Stone 2 can battle it out to see who will reign supreme! Allow your friends to download the trial version of Power Stone 2 from a single UMD.
Wacky new weapons join the existing arsenal of both titles for added comical mayhem.