The mutant turtles were in full battle against Shredder, using all their skills and weapons to try and take him down. But Shredder was faster, stronger, and far more ruthless. Every blow they threw was blocked with ease, and every move was anticipated by their enemy. Just when it seemed like Shredder was going to finish them off, a figure appeared from the shadows. It was a masked woman, dressed in a Foot Clan ninja outfit. Without saying a word, she launched herself at Shredder, surprising both him and the turtles.

"Who is she?" Donatello asked, impressed by the woman's speed and precision.

"I don't know, but she's on our side for now!" Leonardo replied, taking advantage of the distraction to regroup with his brothers.

The mysterious ninja managed to stun Shredder with a couple of quick moves, giving the turtles the time they needed to escape. As they ran away, Leonardo couldn't help but comment, "This isn't the first time that woman has saved us. Remember the ambush with the Krang, or when we almost fell into the Foot Clan's trap."

"Yeah," Donatello added, "she always seems to show up just in time to bail us out of trouble. She's probably using the Foot Clan suit to infiltrate and foil Shredder's plans."

"But why?" Raphael asked, still upset that he hadn't been able to defeat Shredder on his own. "What's in it for her?"

"I don't know," Leonardo replied, "but we owe her one. Without her, we wouldn't have gotten out of this."

Michelangelo, still recovering from the shock, added, "I hope she's on our side... because if not, we're in trouble!"

As they ran through the sewers, the turtles couldn't help but wonder who this mysterious ninja was and why she had decided to help them. One thing was certain: they were more than grateful for his help, but doubts about his true intentions still lingered in their minds.