After lunch, Hayami got up and grasped her sword. "Only two more forms to demonstrate and so many trees not yet recovered. That's a shame."
Practicing Total Concentration Breathing and making sure her stance was perfected, she began to recite aloud, "Eleventh Form: Breaking Avalanche!"
She twirled around like a top, careful not to make herself too dizzy as she performed the attack. Once up in the air, Hayami struck violently. While still in motion, using all of her upper body strength, she let out a breaking blow.
Afterwards, she landed on the ground, exhausted. "How am I to use that in a battle if I get exhausted right now!?"
Tanjiro put a hand on Hayami's shoulder. "Don't worry, Hayami. You'll get there. You're still learning."
Hayami pushed Tanjiro's hand away. "Learning!? Learning!? Learning my ass! I have spent all my time perfecting the move, studying the movements! Do you understand? I mastered it!"
"Mastering doesn't mean there's still learning to take place," said Tanjiro. "Try to heal yourself and try again."
Hayami took a deep breath and allowed her katana to move to the healing position. "Ninth Form: Ice Healing…" she said weakly.
In an instant, she began healing rapidly. Just after a few seconds, she was ready to jump back in. "That takes a really bad toll on my body," Hayami said.
"Maybe we should take a break," Tanjiro suggested.
"I don't want to take a break! Breaks are for quitters!" Hayami said. "If I wanna learn how to make my body stronger, then I need to train more!"
"Don't tire your body out. That's not good for a girl," Zenitsu said.
"Dad! I know when to take breaks! I'm not that dumb," Hayami said.
"But you're showing us that you don't know when to take breaks. Right now we feel it's necessary for you to take a break. If your body cannot handle the attack, please take a break to recover," Tanjiro said. "It's only healthy."
"I don't care about healthy or unhealthy right now! All I want is my body to be stronger!" Hayami shouted. Like a two-year-old, she stomped her foot on the floor.
"It's coming," Tanjiro said. "The teenage years."
"But she's just ten," said Zenitsu.
"She's throwing a fit, Zenitsu. She's getting there," Tanjiro said.
"So she is. Let her be," Zenitsu said.
"What the hell!? Just let her be!? No, no, no. On the contrary, we should intervene and tell her that it is OK to take a break if she needs one," Tanjiro said. "I'm going up there and telling her myself, goddammit."
Hayami threw off her uniform and changed into more comfortable training clothes. While doing so, Nezuko stood in front of her so that Tanjiro and Zenitsu could not see her.
"I'm ready to train," Hayami said. "Now what do I have to do first to get my body stronger?"
"She wasn't kidding, was she?" Tanjiro said. He smiled, putting his hands on his hips. "Eh, what the hell?"
Hayami was then instructed to run from the woods to home every day from then on, as well as lift some weights. She did that every day, making sure to take breaks in between if she needed them for rest and water. Every day until it was the day of her twelfth birthday.
"Nice work, Hayami!" Tanjiro exclaimed. "Now I feel as if all that hard work has paid off, don't you?"
Hayami crouched down, holding onto her knees and heaving to catch her breath.
"Slow down, Hayami. Breathing heavily isn't good for you," said Tanjiro. He smiled, holding up a present. "I hope you haven't forgotten what day it is today."
Zenitsu and Nezuko also held up presents.
Hayami looked around. "With those things, I never would've forgotten. I'm twelve today," she said. "Damn, that's quite a big accomplishment." She smiled. "Hey, and there's even twelve forms! Hey, do you think that once I'm thirteen, I'll be the youngest Demon Slayer to ever exist?"
Tanjiro, Zenitsu, and Nezuko chuckled.
"Maybe," said Tanjiro. "But first you've gotta celebrate your birthday. The day Nezuko had you."
"Ew! Gross!" Hayami cried. "I didn't need to know that detail!"
"Well, that was the day the birds and the bees decided to gift us with you!" Zenitsu said, frollicing around the training grounds.
"Stop it. It's disgusting," said Hayami. "So disgusting I'd rather barf than open whatever you got me."
She sat down on the ground and opened the three presents one by one. One was a new haori. She's never had a haori before and this was gonna mark the event of her becoming an official member of the Demon Slayer Corps. Another gift was a new sword - a better sword than the one she had before. It was long and had a sharp blade like her other katana, but it was so much better. Hayami felt like this one resonated with her more.
She opened up the last box, which was from Nezuko. She was surprised to find a new uniform as well. Happy with everything, she raced up to Tanjiro, Zenitsu, and Nezuko and hugged each and every one of them.
"I'm so glad you agreed to marry both siblings, Dad," Hayami said to Zenitsu. "Because you're the best family I could ever have."
"But the thing is, I didn't marry Nezuko since that would be incest," said Tanjiro. "As a matter of fact, I only agreed to marry Zenitsu, who then agreed to marry both of us."
"Stop talking," Hayami said, putting a finger up to her lips. "Shh."
Raising up her new katana and throwing on her new Demon Slayer Uniform, Hayami confidently arranged her footing and called out, "Eleventh Form: Breaking Avalanche!"
But this time no issues came to her. Her body was fine due to the intense training and she thanked herself for it. She thanked Tanjiro, Nezuko, and Zenitsu for it, but mostly Tanjiro. The training would not have been possible if Tanjiro were not there guiding her throughout. Without him, she would not have gotten as far as she had gotten. If it were not for the book on Ice Breathing, she would not have mastered all twelve forms. She had come so far, and damn, was she proud of herself.