This is not the usual modern open world standard. Instead, you'll be trying to dominate Steel Port, a fictional city where the Saints became more popular but not without competition. Morning Star is one, identified by red and black color. Luchadors is basically Mexican wrestlers with the green clothing theme. Mascots with the crazy and bizarre characters. And there's a blue and white sci-fi villains with girls going speed crazy.
The Saints is known as a small group that made its name from the fictional Stillwater, having purple as their main color. In the last few games, your a protagonist who strives to beat the bad guys and gain allies throughout the story mode. It can be male or female depending on customization and even having a zombie voice is also available. Yikes!
If there is one difference between GTA series and the Saints series, it's the humor that sets the tone for the game. GTA is about bad guys going to war and dominating the land. The Saints might be the same thing but if there's enough turns and twists with the story, there's bound to be a lot of exciting memorable moments and cheesy lines that would keep it from having a dull moment. For example, if you ever want to ride with a tiger, there's one mission that allows you to do just that. Or join a Japanese style game in shooting down mascots. Or perhaps going naked while saving girls in jail while thankfully, the rude parts has been blurred for the fun of it.
Anyway, if you're kind of a gamer who is new to this, or a Saints fan or someone who is looking for a unique game to play, you don't need the knowledge of the Saints series, you just play through the game for its signature humor that makes this game three times the charm.