Deku and Kia broke through, fighting Overhaul, and unfortunately, Deku didn't see her coming.
Kuri launched herself at Overhaul, screaming, "You MONSTER!"
"Kuri don't!" Deku cried, lacing his voice with the power of One for All.
Kuri halted, snarling. "Very well. One for all." Kuri spat the words at him and stood down, sitting down to meditate, taking every bit of the pain Kia has ever suffered.
Deku returned to the fight, not seeing the next attack coming.
"Haissaikaiiii! Binding feathers!" Kuri bound him with her feathers and landed on his back.
Overhaul tried to fight her.
"Kuri!" Deku cried, but she was beyond his voice.
Kuri slapped her hands on his head, using her quirk. "Feel it you sick fuck. Feel what my sister felt at your hands! You self righteous asshole! Feel it till your heart stops!"
The air was filled with horrible screams.
"Kuri stop!" Deku grabbed her. "That's enough!"
But still his words had no effect.
"Wait!" Kia cried from his back. "Don't touch her! Your anger will kill him! Let me help you! Let me help! Deku, she's my big sister!"
Deku took deep breaths, calming down. "Thank you Kia."
"I'm gonna bind you together so your in her head. Tell me when you get there."
Deku took another deep breath and nodded. "Okay. Will do."
Kia bound them together.
"Woah…" Deku could feel her again, their bond repaired and perhaps, even stronger. "Y-yeah I'm good."
"Stop her!"
"Kuri! Stop! Now!"
Finally, Kuri heard him, and halted her attack. "I'm so sorry zu… I didn't finish him off…" Kuri passed out.
Kia pulled on him. "Deku…don't think bad of sister…when she strips a quirk she has to soak up all of the horrible things he's done. His sins give her the power to destroy the quirk…that wasn't my sister, it was Overhaul at his worst. His emotions, his malice, overwhelmed her and took control. She needs you, to remind her who she is."
Deku pulled her close. "I'll make sure she is reminded. I don't think bad about her. I just…I was scared for her…"
"You're gonna be my big brother?" Kia looked hopefully at him.
"Y-yeah I am." Deku blushed.
"Hmm…ok. But if you keep making sis hurt I'm gonna blow you up!"
With her blonde hair and comment, Deku was reminded horribly of Bakugo.
Deku groaned. "Don't do that…don't sound like Kacchan!"
Kia giggled. "Your funny." She kissed his cheek. "Thanks for everything big brother! Get married to sister super soon, ne?"