If Ren could choose one technique to gain an autonomous activation ability, he would select the Substitution Jutsu without hesitation.
Its current activation time was only 0.2 seconds. Against most academy students and ordinary Genin, that was nearly instantaneous.
But nearly instantaneous was not the same as truly instantaneous.
An enemy with exceptional speed might detect the chakra fluctuation and interrupt the technique before the exchange was completed. Its success also depended heavily on Ren's condition. If he were immobilized, rendered unconscious, caught inside a sealing barrier, or deprived of a suitable substitution target, the technique could fail.
That was the fundamental difference between Ren's enhanced Substitution Jutsu and true space-time ninjutsu.
The Flying Thunder God could transport its user to a marked location almost instantly. Amenotejikara could exchange the positions of targets across space with terrifying speed and precision.
Ren's technique merely imitated a fraction of that freedom.
However, if the Substitution Jutsu could sense mortal danger and activate independently, even when Ren failed to react, it would become a genuine life-saving ability.
A blade approaching from his blind spot could be avoided automatically. A fatal ambush might trigger the exchange before he consciously understood what was happening.
The possibility was too valuable to ignore.
Healing Technique's intervention had revealed that the system contained hidden functions it had never bothered to explain. Perhaps autonomous activation was connected to favorability. It might also depend on the technique's personality, its current stage, or a specific emergency condition.
Once his immediate training schedule became less chaotic, Ren intended to investigate the mechanism properly.
For now, he wanted only three things.
A hot bath, a large meal, and several uninterrupted hours of sleep.
"Uncle Duy, I think we should stop here for today," Ren said, rubbing his aching temples.
His chakra had been thoroughly drained by the Eight Gates encounter. Healing Technique had eased the damage to his muscles and chakra pathways, but it had not restored the energy he had already consumed.
At most, his reserves had recovered to thirty or forty percent.
His body no longer felt as though it were about to collapse, but every limb remained heavy.
Duy studied him for a moment before nodding.
The man was fanatical about training, yet he was not careless. He understood that Ren had attempted a forbidden technique for the first time after already completing an extreme endurance exercise. Forcing him to continue would cause injury rather than improvement.
Guy also accepted the decision without complaint. Despite his endless enthusiasm, he had been trained well enough to recognize the difference between pushing through fatigue and recklessly damaging the body.
They rested until Ren could walk without stumbling.
By then, the sun had already disappeared behind the trees. The last traces of orange light faded from the sky as darkness settled over the forest.
The three packed their water bottles, ointments, and remaining soldier pills before beginning the journey back to Konoha.
Duy's voice had become hoarse from cheering all afternoon, but that did not stop him from raising one fist toward the darkening sky.
"The body may tire, but burning youth never ends!"
His roar echoed through the forest.
Several birds that had only just returned to their nests immediately fled again.
Ren and Guy followed him toward the village, both too exhausted to respond with the enthusiasm he expected.
By the time Ren reached home, his appetite had returned with terrifying force.
He ate enough for two ordinary meals and still considered asking for more. After dinner, Aoi gathered the dishes and carried them into the kitchen while Ren forced himself to remain seated long enough for his stomach to settle.
The bath came next.
Warm water loosened the stiffness in his shoulders and washed away the dried sweat and dirt covering his body. Ren remained in the bath until his fingers began to wrinkle and the water lost most of its heat.
Afterward, he returned to his bedroom and opened the medicine he had purchased from the Nara clan's pharmacy.
He applied Tendon-Soothing Ointment around his knees, shoulders, elbows, and ankles. Once the medicine had warmed against his skin, he slowly massaged it into the strained areas.
Next came the recovery exercises Nono had taught him.
Ren completed two careful sets, moving slowly enough to avoid worsening the damage. He finished by drinking a cup of warm milk and sitting on the edge of his bed.
Before sleeping, he tried activating Healing Technique.
Pale-green chakra gathered around his hand.
Ren pressed it against his thigh and guided the energy into the aching muscles. The treatment reduced the soreness, but the effect was nowhere near as smooth or powerful as the technique's autonomous intervention.
When Healing Technique acted independently, its chakra had flowed through him like warm water, locating every strained fiber without conscious guidance. Ren's own attempt felt clumsy by comparison.
The problem was most likely proficiency.
Ren could use the technique, but Healing Technique understood herself far better than he understood her. If he wanted to reproduce that level of treatment, he would need more practice and a deeper knowledge of the human body.
That realization changed his training priorities.
Until now, he had focused primarily on offensive and survival techniques. Great Fireball Jutsu and Wild Water Wave gave him reliable elemental attacks, while the Substitution Jutsu provided mobility.
Healing Technique had received less attention.
That might have been a mistake.
As Ren's physical training intensified and the Eight Gates placed greater strain on his body, medical ninjutsu would become increasingly valuable. A stronger Healing Technique could shorten recovery time, prevent hidden injuries, and perhaps allow him to train at a level that would otherwise destroy his body.
He decided to move her ahead of Great Fireball Jutsu and Wild Water Wave in his training schedule.
The techniques reacted faintly within his mind, but Ren was too tired to invite another argument.
He pulled the blanket over himself and closed his eyes.
"Good night, Transformation Technique. Clone Technique. Substitution Jutsu," he murmured. "Good night to everyone else too."
Several sleepy responses drifted through the Affinity List.
Ren was unconscious before he could distinguish them.
---
"Minato, you're back."
Early the following morning, Hiruzen Sarutobi sat behind his desk in the Hokage's office.
Stacks of reports covered the polished wooden surface. Some contained routine mission records, while others bore seals indicating intelligence too sensitive for ordinary shinobi to access.
The document in Hiruzen's hands belonged to the second category.
Minato Namikaze stood across from him, still wearing his travel-stained flak jacket. He had not yet reached twenty, but his calm presence and sharp blue eyes already distinguished him from most shinobi of his generation.
Two other shinobi stood beside him.
Akimichi Dodo was broad-shouldered and visibly exhausted from the journey. Inuzuka Agari carried the dust and scent of several days spent traveling beyond the Land of Fire's borders.
All three had returned to Konoha less than an hour earlier.
Hiruzen silently turned another page.
The report described unusual movements within the Land of Lightning. The Hidden Cloud had begun purchasing large quantities of metal, medicine, preserved food, sealing materials, and military supplies.
Transport caravans were being redirected toward forward bases.
Shinobi patrols near disputed borders had increased.
None of those actions alone constituted proof of an imminent invasion. Taken together, however, they formed a troubling pattern.
Hiruzen placed the final page on his desk.
"As expected, the Hidden Cloud has begun preparing for war," he said. "The volume of supplies is far beyond what they would need for routine border security."
His expression darkened.
"Their ambitions are not small. A storm is approaching."
The three shinobi remained silent.
Each understood what that conclusion meant. If Kumogakure was preparing for a major conflict, the other hidden villages would respond. Alliances would shift, border incidents would multiply, and minor disputes could ignite a war that consumed every great nation.
Hiruzen looked at them in turn.
"Minato, Dodo, Agari—you performed well. This information may give Konoha the time it needs to prepare."
He closed the report and pressed one hand against its seal.
"Your mission is complete. Return home and rest. I will discuss the intelligence with the village advisers."
"Yes, Lord Third," all three answered.
Dodo and Agari turned toward the door.
Before Minato could follow, Hiruzen spoke again.
"Minato, remain for a moment. There is something else I would like to discuss."
Minato exchanged a brief glance with his teammates and nodded.
Once Dodo and Agari had left, the office door closed behind them. Hiruzen waited until their footsteps faded before reaching for his pipe.
"Do you remember our previous conversation about assigning you as a jōnin instructor?"
Minato considered the question.
"It is almost graduation season at the academy," he said. "Are you planning to place a new Genin team under my command?"
He straightened slightly.
"If that is your decision, I will accept the responsibility and guide them properly."
Serving as a jōnin instructor was not always a desirable assignment.
Training inexperienced Genin required patience and constant supervision. The instructor had to limit the missions they accepted, protect the children from threats beyond their ability, and take responsibility for every mistake the team made.
Many experienced jōnin preferred assignments that allowed them to operate alone or beside equally capable shinobi.
For Minato, however, refusing was never a serious option.
Hiruzen was the teacher of Jiraiya, and Jiraiya had trained Minato. That connection made the Third Hokage more than merely his village leader.
Minato also hoped to become Hokage one day.
A shinobi who wished to lead the village needed to prove that he could nurture its next generation.
"There is no need to decide your team yet," Hiruzen said. "Assignments will be made after the graduation results are finalized."
He lit his pipe, took a slow breath, and allowed the smoke to drift toward the ceiling.
"However, there is one student among this year's graduates whom I want you to observe."
Minato's attention sharpened.
Hiruzen opened a drawer and removed a thin academy file.
"His name is Ren. He comes from a family without the backing of a major clan, and our investigation found nothing questionable in his history."
Hiruzen placed the file on the desk.
"His academic results are excellent, but that is not what makes him unusual. He possesses a unique understanding of the Three Basic Jutsu and has developed an improved version of the Substitution Jutsu."
Minato glanced at the file but did not touch it yet.
"Improved in what way?"
"No advance preparation, no visible hand seals, and almost no delay," Hiruzen replied. "He can exchange positions with an object within range through thought alone."
Minato's expression changed.
Hiruzen continued before he could speak.
"I attempted to reproduce the method. I failed."
That statement carried far more weight than the description of the technique itself.
Hiruzen Sarutobi was known as the Professor because of his mastery over Konoha's vast collection of ninjutsu. If he could observe a basic technique and still fail to reproduce its altered mechanism, then it was not an ordinary modification.
Minato's eyes narrowed.
"Could he have unknowingly incorporated space-time nature transformation into the technique?"
The question sounded impossible even as he asked it.
Space-time ninjutsu was among the most difficult disciplines in the shinobi world. Minato had spent years studying the Flying Thunder God, a technique created by the Second Hokage.
The idea that an academy student had stumbled onto the same field through the Substitution Jutsu defied common sense.
"That is what I want you to determine," Hiruzen said.
He tapped the academy file once.
"The instructors suspect that Ren may possess an unusual aptitude for space-time ninjutsu. Several days ago, he fought a private match against Hyūga Hizashi. I observed part of the battle using the Telescope Technique."
Hiruzen's eyes became thoughtful.
"Ren used a thrown kunai as an exchange point and appeared behind Hizashi before he could complete his defense. It resembled the Flying Thunder God closely enough to deserve investigation."
Minato finally picked up the file.
A small academy photograph of Ren appeared on the first page, accompanied by his written scores, practical evaluations, and instructor comments.
"I understand," Minato said. "I will examine the technique and determine whether it involves space-time ninjutsu."
His voice had taken on the solemn tone he normally reserved for high-level missions.
Hiruzen smiled.
"This is only an assessment. There is no need to approach it as though you are infiltrating an enemy village."
Minato relaxed slightly.
"Do you want me to meet him directly?"
"Decide on the method after you have rested. The academy will cooperate with whatever test you arrange."
Hiruzen leaned back in his chair.
"If Ren truly possesses the talent required to learn the Flying Thunder God, guiding him would be of great benefit to Konoha."
For the first time, the village's greatest living space-time specialist had turned his attention toward Ren.
Minato closed the file.
"I'll handle it carefully."
"Good."
Hiruzen exhaled another stream of smoke before picking up a different report.
"There is one more matter. I would like your opinion."
Minato waited.
Hiruzen's expression became weary.
"Kakashi has received another complaint from his teammates."
Minato's shoulders lowered slightly.
"What happened this time?"
"The mission was completed," Hiruzen said. "The team was not."
Minato looked at the report in Hiruzen's hand and released a quiet sigh.
Kakashi's talent had never been in question. His ability to trust others was another matter entirely.
Outside the Hokage's office, the village continued waking as though nothing had changed.
Minato's return caused little public excitement. He had not yet earned the name Yellow Flash, and his reputation among ordinary villagers remained far below that of the Sannin or the late White Fang.
The intelligence he carried was even less visible.
Kumogakure's preparations were classified at the highest level. No announcement appeared on the mission board, and no warning was delivered to civilians.
Yet secrets of that size always produced ripples.
At Konoha Hospital, storage rooms began filling with bandages, medicine, blood-replenishing pills, and emergency surgical supplies. Experienced medical-nin were quietly reassigned to new shifts. Empty rooms were cleaned and prepared despite there being no patients scheduled to occupy them.
Ren and Rin noticed.
They had visited the hospital often enough to recognize its normal rhythm. That morning, healers spoke in hushed voices, orderlies moved sealed crates through rear corridors, and senior staff repeatedly checked lists of equipment meant for mass-casualty treatment.
No one mentioned war.
No one needed to.
Rin watched another cart of medical supplies disappear through a restricted door. Ren followed it with his eyes, a cold unease settling in his chest.
The storm had not yet broken over Konoha—but the village was already preparing for the wounded it would bring.