Jason is our main character. You can fit him with unique outfits and equipment once they're acquired.
There is also the option of changing the character's whole look and playing as Jessie (who can be found in a separate section of the Shop) or Mei (who can be found as a reward for the Battle Pass season). Jessie and Mei share the same items, skills, trophies, etc. as Jason, besides his clothes. When you start a Story mission as Jessie or Mei, the character's look will automatically be swapped to Jason for the duration of the mission.

There is also the possibility of temporarily changing a character's look. With the Mind-Control Van, you can take control of any character in the city and play as the main character. Please note that you can't access your weapons in this state.