The new rating follows a PC rating from the Game Rating and Administration Committee of Korea back in May.
Here is the ESRB’s description of the game:
This is a third-person shooter in which players assume the role of a young survivor battling through a mutant apocalypse. As players traverse the open-world of Sunset City, they use assault rifles and fantastical weapons (e.g., grenade launchers that shoot teddy-bear bombs, guns that shoot fireworks) to kill mutant creatures, robots, and occasional human enemies. Combat is highlighted by frequent explosions, screams of pain, and gunfire. Some explosives cause enemies to be dismembered, leaving limbs around the environment; one cutscene briefly depicts a character’s head cut off by a mutant. During the course of the game, characters and environmental elements reference sexual behavior or humor (e.g., “Oh, such a bold statement! It says, ‘I am a prostitute!’” and “How hard was it to make a porn flip book?” ); a radio ad contains a running joke about a sex burger (e.g., “It’s so good you won’t be able to contain your urges to rub it all over your Sex…Burger”). The dialogue contains a handful of drug references (e.g., “You guys have been eating weed” and “Oh, when I get back with your drugs, we’ll discuss my offense at your assumption that I would know where to find drugs”). The words “f**k” and “sh*t” also appear in dialogue.
Sunset Overdrive launched for Xbox One in October 2014. A PC version has yet to be announced.
Update 11/05/18 at 6:41 p.m.: An entry for Sunset Overdrive has appeared on SteamDB.
Update 11/08/18 at 9:00 a.m.: Windows 10 achievements have for Sunset Overdrive have appeared on Exophase.