A Step on Both Sides | A KNY Fanfic

Chapter 9

Akaza leaped towards Tanjiro, aiming for his head, while Fumiko did nothing but watch. "Flame breathing, second form: rising scorching sun!" Rengoku said, doing an upwards vertical slash which made Akaza fly back.
Akaza grinned at Rengoku, then scanned the area and saw Fumiko. Their eyes locked. His grin dropped into an open mouth.
"Fumiko, watch out!" Rengoku called.
At the same time, Akaza said, "Fumiko? Is that really you?"
"Father?" Fumiko said, walking towards Akaza. He did the same.
"It is you!" Akaza said. "Where have you been? And why are you wearing the demonslayer uniform?"
"There's a lot to explain, dad. I would like to say it just once, to everyone," Fumiko said.
"We need to get you back to the Infinity Castle as quickly as possible then," Akaza said. 
"Fumiko, how do you know this demon?" Rengoku asked. "He can't be your dad. I've known you for 20 years now. He can't possibly-"
"But Rengoku, I'm half demon," Fumiko explained. "I was born 600 years ago."
"Traitor!" Tanjiro yelled, getting his blade out, dashing towards Fumiko. "I trusted you! I trusted you! You're a fake hashira, that's what you are!"
"You're a hashira now?" Akaza asked. Fumiko nodded.
"You have grown so much... come back, Fumiko. Come back to us," Akaza said.
"Of course, dad," Fumiko replied.
"No! Fumiko!" Rengoku yelled. "Stay with us!"
"I'm sorry," Fumiko said, walking away with Akaza. "I'm sorry."
As the sun started to rise, Akaza turned and ran. He and Fumiko stayed in a cave until nightfall, when they ran to a house. Akaza leapt onto the balcony, Fumiko staying put. She saw Akaza starting to bleed, and jump down.
"Come," he told Fumiko. She followed him onto the balcony, Akaza still bowing, Fumiko looking straight ahead into a child's eyes.
"Dad, who is this kid?" Fumiko asked.
"Fumiko?" The kid asked. "It is you, correct?" The kid...
He had Muzan's voice.
"No way... Muzan?" Fumiko asked.
"Fumiko... you're alive!" Muzan said, turning back into his usual form. "Where have you been? No, I can see where you've been. Why there? How did you get there?"
"Is Kokushibo here?" Fumiko asked.
"Can we go back home, master?" Akaza asked.
"Yes. Nakime," Muzan said, and they got in the Infinity Castle.
"Nakime, summon Kokushibo," Muzan ordered. Obediently, she did as told and Kokushibo stood before them.
He took one look at Fumiko and said, "So this... is why... I am here."
"So I'm gonna explain everything to you guys real quick," Fumiko said. "So when-"
"Hold up guys!" a voice said from behind them. "Aren't you going to tell me too? I so very want to know!"