Gu brought a thicker stone weight to the alcove and set it on the mat beside the two split pieces from the first trial. He checked the boards at its base, then leaned his shoulder into the weight to see whether it shifted.
“Why a thicker one?” Yan asked.
“The first weight had an old seam. We learned the method works, but not how much force you can direct.”
“You want a cleaner test.”
“I want to know where the force goes.” Gu stepped away from the stone. “If it cracks the floor, that is a different lesson.”
Yan stood over the weight. Its surface was rough and gray, with no obvious seam. He set his feet as Gu had taught him. The first circulation had strengthened his marrow and bones. It had not made the stone less solid or the impact less real.
“Small charge,” Gu said.
Yan gathered qi below his navel. The Ashen Marrow route came easily now. He guided the force through the measured breaths, let it collect behind his shoulder, and released through his arm.
His fist struck the stone. The force snapped through his bones and into the target. The weight broke in two, one half toppling against the mat.
Yan laughed aloud. The marrow strain that should have weakened him became another steady warmth through his bones. His frame felt firmer, as if the force had packed the structure closer together. He turned his wrist and flexed his fingers, expecting no hidden ache. Nothing hurt.
“Did the floor take any of it?” Gu asked.
Yan crouched and checked the mat. One board had shifted but the floor was whole. The stone fragments had not cracked the alcove.
“No damage here.”
“Then look at the fracture.”
Gu was less interested in Yan’s grin than in the split. He turned the pieces and traced the break with charcoal. “The angle changed the line. And the chip.” He picked up the loose fragment with a cloth so its edge would not cut his fingers. “The force kept moving after the stone opened. You stopped your arm, but not the impact.”
Yan looked at the white nick in the wall. “Should I release earlier?”
“If you release before the target, you lose the strike. If you release after contact, the remaining force still goes somewhere.” Gu drew a short line across the mat. “Show me the motion without qi.”
Yan returned to his stance and moved through the route slowly. At the turn, his shoulder pointed toward the alcove wall instead of down the target line. He shifted his back foot. The line through his hip, shoulder, and fist turned inward.
“This way?”
“Better. The target changes the angle. Your body has to meet it before the strike, not during.”
Yan repeated the movement once, then stepped away from the stone. “I won’t test that angle again until the next surface is fixed.”
Gu added the new direction to his notes. “That is why we check the cracks before choosing a stronger target.”
Gu looked at the wall, then at Yan. “That chip is mine to repair.”
“I can fix it.”
“You can help me carry the patch plaster. I’ll mark the repair in the alcove log.” Gu wrote down the impact point and the chip’s direction. “The force remains real. The System changes the cost inside your body, not what happens to a wall.”
Yan picked up the chip. It was small, sharp-edged, and heavy in his palm. “I’ll remember where it went.”
The crack and the laughter brought two apprentices from the yard. They peered around the alcove door at the broken weights.
“Did he break those?” one asked.
“Is that a forbidden technique?” the other said.
Gu blocked the doorway with one arm. “It is a supervised lesson. You are not to copy it from the door.”
The first apprentice stared at Yan. “Could you break the furnace gate next?”
Yan set the stone chip down. “The gate is heavier, and the yard would charge me for the damage.”
The apprentices exchanged a look. Gu pointed back toward the yard. “Go ask your supervisor to assign you work.”
They left, still looking over their shoulders. Yan smiled as he swept loose grit into a pan. “They were impressed.”
“They were curious. That is not the same as understanding.”
“They understood the wall was chipped.”
Gu gave him the pan. “Then help me carry it out.”
After the morning lesson, Yan returned to his assigned shift. The marrow warmth stayed even as he sorted metal and carried small baskets. He did not test the technique on work equipment. When the shift ended, he brought the promised plaster and helped Gu patch the white nick in the wall. The repair was rough, but the chip no longer caught on a sleeve.
“What should I use next?” Yan asked. “Something I can control without bringing the alcove down.”
“There is an old practice slab with a replaceable face. It was made to receive strikes.”
“Then let me try it after my shift tomorrow.”
Gu looked at the patched wall. “One low charge. We mark a narrow target line. If you hit outside it, we stop and inspect the face.”
Yan glanced at the wall. “I can split the slab without chipping the alcove.”
“Are you betting?”
“A bowl of dumplings.”
Gu folded his arms. “You pay if you miss.”
“Then I’ll pay.”
“I accept.” Gu took a piece of charcoal and marked the target line on a scrap of wood. “We’ll use the slab after your next assigned shift.”
The following day, Yan returned to the alcove with his shift dust still on his sleeves. Gu had mounted the replaceable face against a reinforced frame. The target line ran across the center. Yan checked the braces, then touched the edge to see whether it rocked.
“It’s steady,” he said.
“Now you have to be.”
Yan took his stance. He gathered a small charge, followed the breath count, and sent the force along the line. The slab separated neatly down its center. No chip struck the wall.
Gu examined the line, then handed Yan a small purse of coins. “The dumplings are paid.”
Yan tucked it away. “I’ll order the largest portion.”
“Of course you will.”
Yan watched the slab pieces rest against the frame. The method had left his marrow stronger, but the target and the alcove still required care. He had learned how much force he could direct at one surface, not how much every structure could bear. He left the pieces where Gu could inspect them and walked toward the market, already planning his dumpling order.