Kanae walked down the steps and came over to them.
"Do you know what 'Total Concentration Breathing: Constant' is?" Kanae looked at the boys before her and explained patiently. "Total Concentration Breathing can enhance your body's functions in an instant. But right now, you can only maintain that state for brief periods during combat. Once you relax, your body returns to normal. 'Constant' means maintaining Total Concentration Breathing twenty-four hours a day, whether you're eating, sleeping, or walking."
Zenitsu let out an incredulous shriek.
"Twenty-four hours?! That'll kill us! It'll definitely kill us! My lungs will explode!"
"If you can't even do that, don't talk about going to the front lines to kill demons ever again." Rokuya's voice came from the roof. He looked down at them, his gaze icy. "Every single Upper Rank under Muzan commands power you can't imagine. Trash who can't even master Constant would only be going there to die."
The three boys fell silent. Inosuke clenched his teeth. Tanjiro's gaze became utterly resolute.
"We're willing to learn," Tanjiro said earnestly.
The hellish training began.
For the next month, the Butterfly Mansion became a purgatory for the three boys.
Kanae guided them through the techniques of Constant. During the day, they had to spar with Kanao while maintaining Total Concentration Breathing. With Constant enhancing her speed and strength, Kanao completely overwhelmed them. Every day, they were beaten black and blue.
At night, they had to practice blowing into gourds. Kanae brought out some specially made, hard-shelled gourds and required them to blow them apart with their breath.
Zenitsu cried and wailed every day. His face turned bright red from blowing, but the gourd remained completely unchanged.
"I can't do this anymore! My lungs really are going to explode! Let me go back to Mount Momoyama!" Zenitsu