In Plazma Burst 2 there are several allies you can get in various levels, and you can play as The Marine, the main protagonist. Proxy, who is a new character in Plazma Burst 2 who you play as in some levels and Noir Lime who was also in Plazma Burst: FttP.They are the main allies in the game however you can find more allies temporarily in various levels, as stated above. You can play as all allies apart from the CS Lites by pressing TAB.
CS Lite Allies
In level 6 you can find a group of soldiers, some Usurpation, and a pair of CS Lites, are trapped in what seems to be a prison. After freeing the CS Lites, they will become your allies however no one else will when you free them. Therefore, it is recommended that you only free the CS Lites. They are not playable (you can't press TAB to play as them, however you can for Proxy and Noir Lime from levels 40 and 41). They start with a Pistol CS-Pro and die fairly quickly.
Android SLC-56 Allies
In level 37, while the main character is Proxy, you can find these allies by climbing up a few platforms next to a few Destroyers and activate the switch. Two Android SLC-56 will teleport in and act as the your allies. They are the fastest character in the game, along with the Android on level 42 who escapes from the CS Base. They have Alien Shotguns though it is unknown how they aquired them. They are the 4th and 5th allies after the CS Lites and Proxy. You are able to play as them.
In level 21, the Marine is cloned, creating the Clone. He will help you thoughout the level using your weapons and armor. In level 22, however, in mere seconds he will start attacking you. In level 21 he is playable by pressing TAB.
From level 30 to level 36 you play as Proxy, possibly the first female character in the whole series. You find different weapons while in the Proxy Campaign and can weild them. Later in the campaign, she allies with the Marine, and then Noir Lime and becomes one of the central allies and main playable characters. She has 500 HP on Easy mode, however if the Marine wears the Heavy Battlesuit, they will both have 750 HP. Along with the Androids, the Clone and Noir Lime, they can be played by pressing TAB.
He was also the main ally in PB: FttP and was left behind by the Marine, however, in level 40 he comes crashing down at the very beginning in a ship, and needs to be revived. He will help in both levels however he only starts with a couple of weapons.