This Trophy comes from Natural Progression
This Trophy is simple, you will no doubt obtain other Person's throughout shuffle time in the game. When you have 5 different ones, simply switch to all 5 in one battle from the combat menu and the Trophy will unlock once you switch to the 5th.
Just don't try it in a boss battle, you may end up getting killed quickly as this does take 5 full turns to do, 1 Persona per turn.