There were two broad forms of the Substitution Technique in the ninja world.
The first was the ordinary E-rank version taught at the academy. Despite its dramatic appearance, it was not genuine teleportation. The user relied on precise timing, rapid movement, and misdirection to exchange places with a prepared object while deceiving the opponent's senses.
The technique was easy to learn and extremely effective against inexperienced enemies.
Its weaknesses were equally obvious.
Its range was short, it usually required preparation, and the moment before activation could be read by skilled opponents. Against another academy student, a well-timed substitution might completely reverse a fight. Against an experienced Chūnin or Jōnin, the same attempt could become painfully predictable.
The second form consisted of personalized replacement techniques created by elite shinobi.
Orochimaru could abandon a damaged body by emerging from his own mouth, almost like a snake shedding its skin. Itachi Uchiha incorporated crows and illusionary misdirection into his evasive techniques, making it nearly impossible to tell when his real body had escaped.
In the hands of such shinobi, substitution was no longer an elementary survival trick. It became a specialized art capable of evading otherwise fatal attacks.
Ren's system had now given him something between those two extremes.
His version retained the academy technique's five-meter limitation and still required a valid replacement medium. However, it removed the two greatest weaknesses: preparation and hand seals.
He could activate it with a thought.
The exchange occurred in two-tenths of a second.
That was faster than most opponents could complete a single hand seal and far quicker than an ordinary person could consciously react. If Ren learned to use it under pressure, he would possess a stable, nearly instantaneous means of escaping death.
The ability was not equal to Sasuke's future Amenotejikara. It could not swap other people or objects freely across a battlefield, nor could Ren exchange positions with anything he pleased.
Still, it resembled a crude, restricted version of that legendary space–time technique.
And this was merely the reward for reaching twenty-five favorability with an E-rank ninjutsu.
Ren closed the status panel and looked at the wooden post across the clearing.
"If the Friendly-stage reward is already this powerful…" he murmured, "what happens at one hundred favorability?"
The thought sent a thrill through him.
Transformation had granted Perfect Form.
Substitution had granted Sealless Instant Release.
If the Three Basic Techniques could produce such extraordinary traits, the Great Fireball Technique's stage reward should be even more impressive.
Perhaps its flames would become hotter. Perhaps the chakra cost would decrease, or the technique would gain greater compression and explosive power.
Whatever the result, Ren wanted it.
"This ridiculous little dating system isn't bad at all."
Of course, it still had limitations.
The [Practice] option did not train for him. It merely allowed his actions to build favorability and helped deepen his understanding of a technique. Every hand seal, failed attempt, depleted chakra reserve, and aching muscle remained his responsibility.
There were no shortcuts around actual effort.
Ren's chakra capacity was also considerably smaller than Obito's. His current Great Fireball was only the size of a large exercise ball and possessed limited range. It could burn someone at close distance, but against a prepared shinobi, it had little practical combat value.
However, even Sasuke—Indra's reincarnation and one of the Uchiha clan's greatest prodigies—had started with a relatively small fireball during his childhood training.
Ren had learned the technique in only ten days.
More importantly, every practice session increased the Great Fireball Technique's favorability. As long as he continued training, both the technique and its system-granted relationship would improve together.
Once its favorability crossed twenty-five, everything might change.
That was the confidence Ren's absurd dating-sim system had given him.
He was weak now.
He did not intend to remain that way.
Ren moved beneath a sturdy tree branch and hooked his legs around it. He had continued his physical routine after completing his ninjutsu practice, finishing sets of inverted sit-ups until his abdomen burned.
He drew himself upward one final time, held the position, and slowly lowered his body. Then he released the branch, twisted in midair, and landed in a crouch.
The movement felt strangely effortless.
Ren bent his knees and jumped.
His body shot upward.
Cold air rushed past his face, and a branch nearly seven meters above the ground appeared directly in front of him. Ren jerked his head aside, narrowly avoiding striking it before gravity pulled him back down.
He landed with both feet planted firmly against the earth.
For several seconds, he simply stood there.
"That was higher than expected."
Ren looked up at the branch. Before awakening the system, he could never have jumped anywhere near it.
He lowered himself into a horse stance and drove one fist forward.
Whoosh!
The punch cut through the air with enough force to stir the mist ahead of him.
Ren rotated his hips and followed with another strike, then another. Each movement felt sharper and more stable. Power traveled naturally from his feet, through his waist, and into his fists.
The three physical attribute points granted by the system had strengthened him comprehensively. His balance, speed, endurance, coordination, and raw power had all improved.
Without a sparring partner, Ren could not accurately measure how much stronger his taijutsu had become.
One fact, however, was undeniable.
The Ren standing in the clearing could easily defeat the person he had been ten days earlier.
He relaxed his stance and checked the position of the rising sun.
"That's enough for today."
Tomorrow was the academy's diagnostic assessment—the final major evaluation before the graduation examination.
Weeks earlier, Ren had decided that its result would determine his future. If his practical performance remained hopelessly average, he would abandon the path of a shinobi and seek work at Ichiraku Ramen.
Now, that old decision felt almost laughable.
He no longer intended to give up.
Even so, the assessment mattered. It would reveal whether ten days of system-assisted growth had merely made Ren feel stronger—or whether he had truly closed the distance separating him from the clan heirs and prodigies around him.
"Ninja or noodle master," Ren muttered, gathering his belongings. "Tomorrow, I'll finally know."
---
The following morning, Ren ate breakfast with his mother and left home earlier than usual.
As he closed the front door, the neighboring gate opened. Rin stepped onto the road with her schoolbag resting against her back.
"Good morning, Ren!"
"Morning, Rin."
She smiled and joined him, but after only a few steps, her expression became puzzled. Her gaze kept drifting toward the top of his head.
Ren eventually noticed.
"Is there something in my hair?"
"No." Rin raised one hand beside her own head, then moved it toward his as if comparing their heights. "Have you grown taller?"
Ren glanced down at her.
Only a short time earlier, he had been slightly taller than Rin. Now the difference approached half a head.
"It seems that way."
"That's strange. People don't usually grow this much in ten days."
"Maybe I've been eating better." Ren gave her an innocent smile. "The fish your family sent must have contained miraculous nutrients."
Rin stared at him for a moment before laughing.
"If a few fish could make someone grow that quickly, every family in Konoha would be standing in the Naka River with a net."
The real cause was undoubtedly the system's physical enhancement.
The three attribute points had not simply strengthened Ren's muscles. They had improved his entire body, subtly accelerating his growth and making him appear healthier.
Fortunately, eight years old was a natural age for sudden growth. His change was noticeable but not alarming enough to attract serious suspicion.
They continued toward the academy.
After crossing the small bridge, Rin's playful expression became more focused.
"Ren, Instructor Oki answered my question about medical ninjutsu."
Ren immediately turned toward her. "What did he say?"
"Konoha Hospital runs an introductory course for new medical personnel. It isn't part of the academy curriculum, but students can audit the lessons if an instructor recommends them."
"And he recommended you?"
Rin nodded, unable to hide her excitement. "I can begin next week."
"That's excellent."
Rin clasped her hands behind her back as she walked. "Would you like to come too? Instructor Oki said he could include you in the recommendation. If we attend together, we can discuss anything we don't understand."
"When are the classes?"
"Weekend mornings. Some additional lessons are held on weekday evenings, depending on which medical-nin are available. Most instructors are Chūnin, but Jōnin sometimes give lectures as well."
Rin paused before adding with obvious admiration, "I heard Lady Tsunade has even taught there in the past."
"Tsunade…"
Ren's first thought was not of the legendary Sannin's strength, but of the impossible standard she had established for every medical-nin who followed her.
Tsunade had transformed Konoha's medical system. Her proposal to assign trained medical shinobi to four-person squads had saved countless lives, even if wartime shortages had prevented the village from implementing the idea universally.
However, by this point in history, Tsunade had likely already left Konoha. The deaths of Nawaki and Dan had left her traumatized, and her fear of blood made regular hospital work nearly impossible.
The chance of meeting her at an introductory class was extremely low.
But not zero.
More importantly, the lessons themselves offered access to knowledge Ren could never obtain through the academy.
"I'll go," he said. "Tell me when the first class is confirmed."
Rin's face brightened. "I will."
A quiet determination had entered her expression. Ren could already see the difference his suggestion had made. Medical ninjutsu was no longer a vague possibility to her. It had become a path she had chosen for herself.
Whether that path would be enough to change her fate remained unknown.
But the first step had been taken.
By the time they reached the academy, the entrance was crowded with students. Excited conversations filled the courtyard as everyone speculated about the assessment.
Some students greeted Rin as she passed. Her patient personality and habit of helping others had made her popular throughout the class.
A boy from the Hyūga clan approached them near the stairs.
His name was Hyūga Daichi, a branch-family child their age. His pale eyes briefly settled on Ren before his attention shifted toward Rin.
"Good morning, Rin," Daichi said, deliberately ignoring Ren. "You shouldn't worry about today's assessment. With your chakra control, you'll have no trouble passing."
"Thank you, Daichi. Good luck to you too."
Daichi raised his chin. "Luck has nothing to do with it. Members of the Hyūga clan are trained from childhood."
His gaze slid toward Ren again.
"Some people might need luck, though."
Ren smiled. "Good morning to you too."
Daichi's expression tightened. He had clearly hoped for irritation rather than politeness.
Like many children from prestigious clans, Daichi possessed a natural pride in his lineage. He was not malicious, but his attempts to impress Rin usually involved boasting about the Byakugan or belittling the other boys around her.
Obito attracted attention through loud declarations and reckless displays.
Daichi preferred to act distant and superior.
Rin found both approaches exhausting.
Ren had become an especially convenient target since Kakashi graduated. His appearance earned him more attention than his mediocre abilities justified, and his familiarity with Rin made several boys view him as a rival.
Ren had never cared.
They were children competing over classroom attention. He had a war to prepare for.
Daichi mistook his silence for discomfort and continued. "Today's diagnostic assessment includes practical combat. We'll finally see how much everyone has actually improved."
"That's what assessments are for," Ren replied.
Before Daichi could respond, the academy bell rang.
Students hurried into the building.
When Ren entered the classroom, the usual desks had been pushed against the walls. Instructor Oki stood at the front beside a large wooden board covered by a white cloth.
The excitement in the room died immediately.
Oki surveyed the students, his expression far more severe than usual.
"Today's assessment will measure your ninjutsu, taijutsu, weapons skills, and combat judgment," he announced. "Your performance will determine whether you remain eligible for next year's graduation examination."
Several students straightened nervously.
Ren felt his heartbeat quicken.
Instructor Oki gripped the edge of the cloth.
"And this year, the practical assessment will follow a different format."
He pulled it away.
A complete list of combat pairings was revealed beneath it.
The classroom erupted in whispers.
Ren scanned the board until he found his name.
The moment he saw the opponent written beside it, his eyes narrowed.
This assessment would be nothing like the easy academy test he had expected.