We know you're out there! If you don't surrender, we start executing hostages!
~ Karai luring the Turtles.
Karai is a supporting antagonist of the 2014 Paramount film Teenage Mutant Ninja Turtles and a minor antagonist of its 2016 sequel Teenage Mutant Ninja Turtles: Out of the Shadows. She is the mission leader of the Foot Clan and the Shredder's assistant.
She is portrayed by Minae Noji in the first film and Brittany Ishibashi in the 2016 sequel.
Karai is the second in command of the Foot Clan. She is the assistant to Shredder and is the one who leads the missions for the Foot Clan. She attempts to draw out the Turtles in the subway by capturing hostages (including April O'Neil), but is subsequently knocked into a wall. Karai assists the Shredder and Eric Sacks various times in the film. During the battle on the mountains, Karai leads the Foot Clan to follow in pursuit of the turtles, until they manage to ram her jeep into a tree.
In the sequel, Karai reappears as the Shredder's right-hand woman and bodyguard. She works closely with the Shredder and Baxter Stockman and is assigned to guard the Technodrome's shield. However, April and Vern arrive and battle Karai and her Foot soldiers, defeating Karai in the process.
This is the first live-action appearance of the character.
This is one of the few times Karai doesn't redeem herself and help the Turtles in some way.
Unlike other iterations of the character, this version of Karai has less of a major role, much to the chagrin of TMNT fans and reviewers.
Karai was going to have more scenes in the first film. In one such scene, she battles April O'Neil in downtown Manhattan, only for Vernon Fenwick to arrive in the nick of time, hit Karai with a gurney, and have April finish her off.
However, the concept of April and Vernon fighting Karai is reused in Out of the Shadows.
Karai is ultimately the secondary antagonist of the series.