There are 2 ways to do this either use action replay or after your have completed the game head towards the dead gods pad Search for the door by scanning and go through it when you get to the final boss zone where you fought that massive dragon thing talk to joshua who will be standing there talk to him There will now be a cutsceene about how that joshua is from another dimension WATCH IT FOR YOURSELF! after the cutsceene get some good pins and put them on prefferably mastered ones
NOTE: If you do this on ultimate you will get at least 3000pts after the battle ( well i did it on that) After all of this make sure you have fushion lv 3 on for all characters as you will be using all of them in this battle
If you think your ready talk to joshua and you will start a chain battle with all the bosses
The order in characters is
Shiki 1st & 2nd
Joshua after shiki
Beat after joshua
After all this is done There wil be another cutsceene Joshua will give you 6 pin slots if beat his battle - Hope this helped