Chakra is made of yin and yang.
Iruka said it the same way he always did—calm, steady, pitched so it carried to the back of the classroom without sounding like a lecture. He stood with his hands resting on the edge of the desk, eyes moving over familiar faces. Naruto was slouched too far back in his chair, trying very hard to look bored. Sakura was sitting straight, attentive. Sasuke looked like he already knew the answer and was mildly offended that it was being explained at all.
"Yin governs the mind," Iruka continued, tapping the side of his head with two fingers, "and yang governs the body. When you mold chakra, you are not creating something new. You are balancing what is already there."
A few students nodded. A few pretended to. Iruka had learned to tell the difference years ago.
He let them try. Hands raised, chakra flickering unevenly, the classroom filling with that faint pressure that always accompanied children attempting to do something their bodies weren't ready for yet. Iruka corrected posture, adjusted hand seals, offered encouragement where he could. It was ordinary. Comfortably ordinary.
When the bell rang, the pressure ebbed. Students filed out in clumps, noise replacing concentration in the way it always did. Naruto lingered just long enough to ask a question that had nothing to do with chakra and everything to do with lunch. Iruka answered it anyway.
By the time the hallway settled, Iruka felt the familiar weight behind his eyes—the quiet fatigue that came from maintaining barriers, projecting calm, and constantly monitoring dozens of small, unstable chakra networks at once. He exhaled slowly, gathering his notes.
That was when he noticed the boy waiting by the doorway.
He wasn't one of Naruto's classmates. Younger. From the adjacent classroom down the hall. Iruka had seen him before, of course—small village, shared corridors—but not often enough to know his name without checking a roster.
The boy bowed, a little too stiffly. His face was pale, skin drawn tight over his cheekbones. There was a faint sheen of sweat on his forehead despite the cool weather.
"Umino-sensei," the boy said. His voice was steady, but thin. "May I speak with you?"
Iruka set his papers down. "Of course. Are you feeling all right?"
The boy nodded immediately, too quickly. "Yes, sensei."
Iruka had learned to mistrust that nod.
"Come inside," he said, gesturing back into the classroom. "Sit down."
The boy obeyed, perching on the edge of a chair as if afraid of taking up too much space. Up close, the signs were clearer. Dark shadows under the eyes. A faint tremor in his hands. His chakra—Iruka focused carefully, politely—was present, but wrong. Thin in places, uneven, like water forced through a cracked channel.
"You've been unwell," Iruka said gently. It wasn't a question.
The boy hesitated, then nodded again. Slower this time. "Just a fever. It's getting better."
"How long?"
"A few weeks."
Iruka felt something tighten in his chest. "Have you been to the infirmary?"
"Yes, sensei. They said I should rest."
"And did you?"
The boy's fingers curled slightly against his knees. "I didn't want to fall behind."
Iruka closed his eyes for a brief moment. He had heard this before. Too many times. "You're still very young," he said. "Your chakra network is still developing. Pushing it while you're sick—"
"I know," the boy interrupted, then flushed. "I'm sorry. I just thought if I refined it carefully… very carefully… it would help."
Iruka opened his eyes and looked at him fully now. The boy wasn't lying. There was no bravado there, no ambition. Just earnestness. Effort.
"What do you mean by carefully?" Iruka asked.
"I practiced after class," the boy said. "Very small amounts. Just holding it. Not using any jutsu. I thought if I could keep it stable, my body would follow."
Iruka's breath caught. He reached out without touching, extending his senses just a little further.
The boy's chakra was circulating.
Not explosively. Not erratically. It was looping.
A tight, repetitive cycle, feeding into itself with no real output. Yin and yang pressed together without release, over and over, like a wheel spinning in place.
"This is dangerous," Iruka said immediately, stepping closer. "You need to stop. Now."
"I can," the boy said, but there was uncertainty in his eyes. "I just need a moment."
"No," Iruka said, sharper than he meant to. "Listen to me. You need to let it go."
The boy nodded—and then stiffened.
It happened too fast and too slowly all at once. His hands clenched. His shoulders locked. The thin chakra loop tightened abruptly, compressing instead of dispersing. Iruka felt it like a wrong note in a familiar melody, a pressure spike that made his skin prickle.
"Hey," Iruka said, reaching out instinctively. "Look at me."
The boy's eyes rolled back.
His body convulsed, chair scraping violently against the floor as he collapsed. Chakra surged—not outward, but inward, folding back on itself in a way Iruka had never felt before. A feedback loop. Closed. Self-sustaining.
"No—" Iruka dropped to his knees beside him, hands glowing faintly as he poured chakra into the boy's system, trying to break the cycle. "Stop. You have to release it. Let it go."
There was no response.
Their chakra networks touched.
Iruka felt it distinctly—the moment his own steady flow brushed against the boy's unstable loop. It wasn't invasive. It wasn't violent. It was like stepping into cold water when you expect warmth. A sudden, visceral awareness that something was wrong at a fundamental level.
The boy's chakra didn't reject Iruka's.
It grabbed it.
Not aggressively. Desperately.
Iruka sucked in a breath as a wave of dread rolled through him, sharp and absolute. Not pain. Not unconsciousness. Just the certainty that he was standing at the edge of something that should not exist.
"Medic!" he shouted, louder than he thought possible.
Footsteps. Voices. Hands pulling him back as the infirmary team rushed in. Iruka let them, his own chakra snapping back into place with a sickening sense of finality. The boy lay still, too still, his chest no longer rising.
Iruka stared at him, numb, as they carried the small body away.
They told him later that there was nothing he could have done. Congenital weakness. Complications from fever. Chakra exhaustion. Words stacked on top of each other like sandbags against a flood that had already passed.
Iruka nodded. He thanked them. He finished his classes.
By the time the Academy closed for the evening, the halls were quiet again. Too quiet.
Iruka locked his classroom and walked home alone, the image of the boy's pale face replaying behind his eyes. The way the chakra had folded in on itself. The way it had held.
His apartment was dark when he arrived. Familiar. Safe.
He slid the key into the lock.
For just a moment—no more than a heartbeat—Iruka was seized by that same sensation of dread again. Not fear. Not panic.
Just the deep, unshakable feeling that something had followed him home.
The lock turned.
The door opened.