Cold was not merely the absence of heat.
That was the mistake most healers made.
To them, Seo Yoon-hwa's condition was simple. A congenital lack of Yang. A weak heart meridian. Something that could be compensated with enough warmth, enough pills, enough time.
They were wrong.
Bing-mu did not consume Yang. It replaced it.
Extreme Yin did not leave emptiness behind. It carved its own order into the body. Where warmth once circulated, stillness took root. Where blood once pulsed freely, clarity hardened into structure.
By the time Hae-jin understood this, it was already too late.
⸻
They traveled south, following rumors of a physician who specialized in Yin disorders. The journey took weeks. Snow gave way to rain, then to damp heat that clung to the skin.
Yoon-hwa endured it silently.
Heat was foreign to her body. Too much warmth made her dizzy. Too little sent knives of cold through her chest. She existed in a narrow space between extremes, and Hae-jin walked that line with her.
The physician lived alone, deep in the lowlands. An old woman with clouded eyes and hands scarred by frostbite.
She examined Yoon-hwa for a long time.
Then she shook her head.
"This is not illness," the woman said. "This is cultivation."
Hae-jin stiffened.
"She was born with it," he argued. "The cold—"
"Was invited," the woman interrupted. "And it answered."
She gestured toward Yoon-hwa's chest.
"Her heart no longer circulates warmth naturally. Yin qi has rewritten the pathways. Even if you pour fire into her every day, it will only delay what has already been decided."
"How long?" Hae-jin asked.
The old woman hesitated.
"That depends on how much you are willing to burn."
⸻
That night, Yoon-hwa sat by the window, watching rain slide down the glass like melting frost.
"You heard her," she said calmly.
"I don't accept it," Hae-jin replied.
She turned to face him.
"Bing-mu requires absolute stillness," she said. "That is why it is powerful. That is why it is cruel. The heart is never still."
He said nothing.
"You warm me," she continued, softer now. "But warmth is movement. One day, my heart will choose stillness instead."
Silence settled between them.
Not heavy.
Just final.
⸻
When they returned north, Yoon-hwa began teaching him Bing-mu theory.
Not the techniques. He could never practice them. But the philosophy.
"Extreme Yin seeks permanence," she explained as they sat together in the snow. "Fire changes. Ice endures."
"And yet," Hae-jin said, "ice melts."
She smiled faintly.
"Only when the fire is stronger than it."
Her hand rested over his chest.
"Your fire is not meant to overpower," she said. "It is meant to accompany."
⸻
The Gu Clan elders summoned him soon after.
They did not shout.
They did not threaten.
They simply showed him the records.
Names of fire cultivators who had overextended themselves. Lifespans cut in half. Meridians scarred beyond repair. Flames that never answered again.
"This is the path you are choosing," the elder said.
Hae-jin bowed deeply.
"I know."
"Then why walk it?"
He lifted his head.
"Because," he said, "if fire cannot protect warmth, then it has no right to exist."
No one argued.
⸻
That winter, Seo Yoon-hwa's heart skipped its first beat.
She did not tell him.
But when his palms rested against her chest that night, the warmth lingered longer than before.
As if the cold had paused—
just to remember what it was losing.