The sidekicks appear in the PC version of Daikatana and the GBC version, and are not used in the 64 version. They are supporting characters that have an impact on gameplay. They function somewhat differently in the GBC and PC version but serve the same purpose, to assist with Hiro's quest and provide dialogue and help throughout the game.
PC Version[]
Mikiko and Superfly appear as sidekicks in the PC version, and become AI controlled companions as they are rescued. As sidekicks, they will fire upon enemies and react to the player's commands, such as back off, and come. The player can ask the companion to get a pickup, and the companion will obtain it. Obtaining a weapon pickup will make the sidekick use it, and obtaining an ammo pickup will make the sidekick get ammo for the weapon. The sidekick will also get health and armor pickups if asked. Sidekicks cannot use interactables, such as berries and Hosportals. Sidekicks will also sometimes decline getting a pickup, for example, if the pickup is unreachable, if asked to get a health pickup at high health, and certain other situations.
You will need all active sidekicks right beside you so you can proceed past area transitions.
To see more info about their behavior, see Sidekick AI.
GBC Version[]
Sidekicks will follow you when you free them. You will switch between characters as the story progresses for certain situations. Sometimes you may need to play as Superfly, or Mikiko along with Hiro. The sidekicks have minor differences, such as not being able to use certain weapons in certain situations.