Kenji reached the Senju estate shortly before dinner, alone as Karin had requested. The house itself was still busy. Guards followed their usual routes around the private wings while servants carried dishes toward the dining hall.
He found Karin outside her bedroom with a sealing brush tucked behind one ear and dark ink covering the tips of her fingers. She looked at him, then leaned into the corridor to make certain nobody had followed.
"You actually came alone. I was half expecting Shizune-san to arrive with a medical bag and declare that testing a private barrier required supervision."
Kenji glanced down the empty hallway. "I left the committee at home."
Karin snorted, caught his sleeve, and pulled him into the room before the committee could change its mind.
Karin closed the door and pressed her ink-stained palm against the spiral painted beside the frame. The footsteps in the corridor disappeared. So did the servants downstairs and the dishes being moved through the dining hall.
Kenji looked toward the door. The estate was still moving beyond the walls, but none of its noise reached the room.
Karin tapped the spiral with one finger. "Sound stays inside. The warning mark lights whenever someone enters through the door or window. A sensor standing close enough can still feel chakra, so it does not make the room invisible. It only keeps private things private."
She stepped away from the threshold and folded her arms. "Try getting past it."
Kenji stepped into the corridor and pulled the door nearly shut behind him. He activated Silent Tread, softened his breathing, and crossed the threshold without letting his clothes brush the frame.
Karin pointed at his chest before his second foot entered the room.
"Caught you."
A heartbeat later, the spiral beside the door flared red.
Kenji glanced from the mark to her finger. "The seal caught me."
Karin adjusted her glasses, looking far too pleased with herself. "The seal confirmed it. I felt your chakra before it lit."
Kenji tested the window next. He climbed onto the narrow roof outside and lowered himself through the opening. The warning spiral lit as soon as his hand crossed the frame, well before his boots reached the floor.
For the final test, he tossed a marked kunai through the open window. The weapon clattered harmlessly across the floor, but the spiral remained dark. When Kenji followed it inside, the mark immediately turned red.
Karin pulled a notebook from her desk and wrote beside one of the diagrams. "It ignores weapons. That is fine for privacy, but not for security. Someone could still throw poison, an explosive tag, or a listening seal through the window."
Kenji stepped fully into the room and suggested that the next version should react to objects carrying chakra. Karin added the correction and underlined it once. Even with the flaw, catching Kenji through both entrances had left her visibly pleased.
Kenji looked over the seals again before returning his attention to Karin.
"It blocks sound, watches the entrances, and keeps working without someone standing outside all night. You built something useful."
Karin's fingers tightened around the notebook. She pressed her lips together and looked down at her notes as though they suddenly required her complete attention, but the smile escaped anyway.
Once Kenji had finished testing the window, Karin released the sound seal. The estate returned all at once—and with it came Naruto's unmistakable voice from downstairs.
He was loudly arguing that three large bowls of ramen still counted as a light meal.
Karin shut her notebook. "He was supposed to leave twenty minutes ago."
She had invited Naruto over after lunch to show him several beginner Uzumaki records from Mito's collection. Apparently, the records had finished before his appetite did.
Naruto sat at the main study table beside a stack of spiral-marked books, three empty ramen bowls, and a fourth bowl the attendant had apparently refused to provide.
He was also wearing a grin far too large for someone who had supposedly spent the afternoon doing ordinary clone training.
Kenji stopped in the doorway. "Productive afternoon?"
Naruto's grin immediately became defensive. "Training went well. That's all."
Karin looked between them as she approached the table. "Was this the Byakugan training?"
"Clone training," Naruto corrected, suddenly finding the open book fascinating.
Kenji left him to suffer and pulled out the chair opposite him.
Karin opened a fragile family chart and showed Naruto the branches connecting the surviving Uzumaki families to the Senju. She explained that the clan had once been famous for seals strong enough to contain chakra, protect villages, and survive for generations after the person who drew them had died.
Naruto ran one finger over the spiral on the page, then glanced at the matching symbol on his jacket. "Everyone was wearing this, and nobody thought to explain it to me?"
Kenji pulled out a chair. "Konoha has never allowed useful information to interfere with tradition."
Naruto stared at Karin. "Does that make you my cousin?"
Karin pushed her glasses higher. "Very distantly."
Kenji looked between the red-haired sensor and the blond loudmouth wearing the same clan spiral. "Konoha finally has enough Uzumaki for a proper family argument."
Naruto leaned over the beginner exercise Karin had written out for him, studying the basic containment circle.
Naruto cracked his knuckles. "That sounds easy."
Karin silently placed six spare sheets beside the first one.
The edges of Naruto's first containment circle caught fire less than a minute later.
Before Naruto could ruin a second sheet, Sasuke arrived at the estate for his scheduled checkup.
In the courtyard, Karin pulled Sasuke's collar aside far enough to place one monitoring strip beside the Curse Mark. A second strip wrapped around his wrist, where she could watch how the foreign chakra moved through the rest of his body.
Sasuke took his position between two wooden posts. At Karin's signal, he used one short Swift Step burst. Leaves jumped from the grass as he crossed the yard and stopped beside the second post.
The movement itself was clean. The reaction beneath his collar was not.
A dark line crept away from the edge of the Curse Mark. Karin was already moving before Kenji had fully noticed it. She pressed two ink-stained fingers against the shoulder strip. The seal lines tightened around the mark, and the spreading pattern stopped. A moment later, the dark line withdrew.
Karin released the seal and shook out her hand. "It feels like snake chakra trying to crawl through someone else's pipes."
Sasuke stared at her. "Never describe it that way again."
"Then stop carrying snake chakra in your neck."
Kenji had barely seen the first dark line before Karin stopped it. Kenji had barely noticed the first dark line before Karin stopped it. Kakashi's seal restrained the Curse Mark, but Karin could feel it stirring before the reaction visibly spread.
Karin recorded one safe burst, one minor flare, and another mandatory check before Sasuke increased the technique. Sasuke read the restriction over her shoulder. His expression made his opinion clear, but he had just watched the seal stop the Curse Mark and did not argue.
Naruto left first with the beginner exercise, two brushes, and the remaining sealing paper tucked beneath one arm. At the gate, he turned and asked whether Karin would check his work the next day.
"Only if you stop calling every crooked spiral close enough," she warned.
Naruto laughed and promised nothing before jogging toward the village center.
Sasuke left next with instructions not to use Swift Step again that evening, to return if the mark began aching, and under no circumstances to activate it deliberately just to see what happened.
"I wasn't planning to," he said.
The look Kenji exchanged with Karin made it clear that neither believed him.
Once the front doors closed behind Sasuke, the estate finally became quiet. Kenji looked toward the staircase. Karin did not explain. She simply turned and led him back to her room.
Inside, she closed the door, slid the ordinary deadbolt into place, and pressed her palm against the spiral seal. The distant movement of guards and servants disappeared again. A low red glow settled into the ink beside the frame.
Kenji glanced at the lock. "The first test didn't require that."
Karin remained with her back against the door. The sealing brush was still behind her ear, and ink covered the fingers she raised between them.
"The first test was for Tsunade's report. This is for me."
She counted each accomplishment on those stained fingers. She had studied Mito's records every day, built the sound barrier and entrance alarm, found weaknesses during the test, stopped Sasuke's flare, and started teaching Naruto without setting the study on fire.
Her hand lowered, but her gaze remained fixed on Kenji. "You told me to become strong enough that nobody could use me again. I am doing it."
Kenji stepped closer. The joking expression left his face without turning the moment into something heavy.
"You are. You didn't copy one of Mito's seals and pretend the work was finished. You changed it for this room, tested it, and wrote down what failed. You felt Sasuke's mark move before the rest of us saw it. Naruto left with an exercise he can actually learn from. That is your work, Karin."
Her fingers caught the front of his jacket. She did not hide the pleased smile this time.
"Then I want the reward you promised."
Kenji stopped close enough that her knuckles rested against his chest. "What do you want?"
Karin took his hand and deliberately placed it against her waist. Her breathing had quickened, but she kept her eyes fixed on his.
"Your full attention tonight."
Kenji left his hand where she had placed it without pulling her closer. "You're certain?"
Karin stepped forward herself, closing the remaining space between them. The active spiral glowed steadily beside the locked door. She reminded him that she had built the barrier, locked the room, and waited until Naruto and Sasuke had left. Nobody outside could hear what happened between them. Still holding his hand against her waist, she tilted her face toward his and asked, "What do you think?"
Kenji's fingers tightened gently at her side.
Karin glanced once toward the sealed door and then back at him.
"Now no one interrupts my reward."
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