The first time Kang Hae-jin collapsed, it was over nothing.
No battle.
No ambush.
No reckless overuse of flame.
It happened during a routine warming session.
Morning light filtered through thin clouds. Snow lay undisturbed around the small wooden pavilion they used for cultivation. Seo Yoon-hwa sat calmly, breathing in measured cycles, frost clinging lightly to her lashes.
Hae-jin placed his palms against her back.
He inhaled.
Nothing happened.
For a brief, terrifying moment, his fire did not answer.
He forced his breath deeper. His dantian stirred sluggishly, heat gathering like embers buried beneath ash. Warmth finally flowed, thinner than usual, slower, but enough.
Yoon-hwa relaxed.
Hae-jin did not.
By the time the session ended, his vision blurred. The world tilted. He managed one step away from her before his knees buckled.
Snow rushed up to meet him.
⸻
He woke to cold.
Not the sharp, disciplined cold of Bing-mu, but the dull, aching cold of exhaustion.
Yoon-hwa knelt beside him, one hand hovering uncertainly over his chest, as if afraid to touch him too much.
"You should have stopped," she said.
"I was fine," he replied automatically.
She did not believe him.
Later that day, Gu Clan elders confirmed what she already suspected.
His meridians showed signs of thermal fatigue. Constant forced circulation against extreme Yin had thinned his fire channels. His flames still existed, but they no longer surged on command.
"Your cultivation is not failing," the elder said. "It is being consumed."
Hae-jin nodded.
"How long?" Yoon-hwa asked.
The elder's gaze softened.
"That depends on how often he chooses you over himself."
⸻
Yoon-hwa changed after that.
She reduced her Bing-mu circulation. She skipped training sessions. She endured the cold longer before asking for warmth.
Hae-jin noticed everything.
"You don't have to do this," he told her one night.
"You don't have to burn yourself either," she replied.
They argued for the first time.
Not loudly. Not angrily.
Quietly. Carefully. Like two people afraid that raising their voices might shatter something fragile.
In the end, neither yielded.
⸻
Winter deepened.
Yoon-hwa's techniques grew sharper despite her restraint. In battle, her ice moved with frightening clarity, freezing opponents mid-step. Yet each victory left her paler, colder.
One night, she returned wounded.
Blood stained the snow dark. Her breathing was uneven. Yin backlash surged wildly, cold radiating beyond her control.
Hae-jin did not hesitate.
He poured fire into her.
Not carefully. Not gently.
Desperately.
Heat surged from his core, flooding her meridians, forcing Yin back through sheer persistence. Frost cracked. Blood thawed. Her heart steadied.
But when it was over, Hae-jin's hands shook uncontrollably.
He could not stand.
Yoon-hwa caught him before he fell.
For the first time, she held him to keep him alive.
⸻
That night, as he slept wrapped in blankets, she sat beside him, unmoving.
She finally understood.
His fire was not weakening because it lacked strength.
It was weakening because it was being spent exactly as it was meant to be.
Warming.
Protecting.
Refusing to burn anything else.
Outside, snow continued to fall.
Inside, the balance shifted again—
quietly, irrevocably.