Agent 4 can have a variety of appearances, depending on the player's choice of gender, skin color, eye color, and hairstyle, as well as their current ink color. They wear the new version of the Hero Suit, and can pick up Armor to wear as well. They wield the Hero Shot by default, but are later able to use a variety of other Hero weapons given to them by Sheldon.
Agent 4 initially went to Inkopolis for an unknown reason, but got swept up in Marie's quest to save the Great Zapfish and her cousin Callie. In Octo Canyon, Agent 4 completes various missions to retrieve stolen Zapfish, defeating many Octarians along the way. Eventually, Agent 4 confronts DJ Octavio and a brainwashed Callie, rescuing the Great Zapfish, freeing Callie, and finally restoring Inkopolis' power supply.