Protagonist (Ren or Akira)
A picture of the protagonist in his Shujin Academy uniform
The protagonist of Persona 5 is the main character which is controlled by the player. In spinoffs and Persona 5: The Animation, he is given the name of Ren Amamiya. Additionally, he has been given the name "Akira Kurusu" in the Persona 5 manga, so there is a bit of debate over what his name should be. The player ultimately gets to name the protagonist however they want, to feel more indulged in the world of Persona.
Codename: Joker
Joker in his metaverse attire
The protagonists alter ego in the metaverse is Joker. Joker does not have a unique persona like the other members of the phantom theives, rather he has the ability to use any persona he has a "mask" for. Although, Arsene, the persona that he first awakens in the metaverse, is commonly shown as his equivalent of a unique persona. With Joker being able to use a multitude of personas, his strength is purely based on how the player chooses. His melee weapon is a dagger, and his gun is just a standard pistol.
History
Before the events of Persona 5, Ren (or Akira) is put on probation and sent off to attend a different school for his actions of assaulting a political figure. The brings him into Shinjuku, to stay in the small attic of a coffee shop, owned by Sojiro Sakura. He is treated by his most of his peers as a screwup, and a danger. His closest friends that he makes ultimately become part of the phantom theives, and help him make changes in the desires of the corrupt.