Main Power Up is a new ability. Here's it's effect for each weapon (as of Version 4.3). Main Power Up effects do not stack very well at all tbh.
I recommend watching in fullscreen if possible.
twitter.com/CptAstro
Music Used:
Maybe I'm a Lion (FFVIII) - The Black Mages
Dancing Mad (FFVI) - Distant Worlds II
Keep Pressing On - Phoenix Wright Ace Attorney: Dual Destinies