Support Personnel (or SP for short) are AI-controlled characters that can randomly join you while doing missions and replace your party members. At the beginning of every mission, players will have the option to refuse or accept help from Support Personnel. Choose to accept and throughout the mission, any party members (not the leader) can be replaced by a black shadow figure that resembles your party members.
These are the SP and are named after the staff in the game, except for three special ones. The special ones are random and one requires you to get an item before he appears; they are Kurasame, his Tonberry and Joker. For the last one, you need to hit Nimbus a total of 30 times for the Special Order at the end of Operation MA Demolition.
Support Personnel Points
You may have noticed that as you use the Support Personnel, that they will give you points. These are Support Personnel Points (SPP for short) and they are accrued by the SP doing things like defeating enemies or healing your characters. SPP has a number of uses in the game, such as using it to buy items in a special shop (located in Central Command in Akademeia) or receiving temporary items once you reach certain thresholds.
SPP: The points you get from the SP during missions will only be awarded to you if they leave the battlefield of their own accord. This happens once they are on the field long enough or if you reach a safe area with a save point/recovery portal. Should that SP die during combat, then you will lose any SPP they may have accumulated.