Hibari had indeed been flustered for a while by his excessively rapid physical growth, worrying that it was too uncontrolled. He feared he might develop an old man's face by the time he was seventeen or eighteen, or even become a decrepit old man in his twenties, which would be truly disheartening.
Fortunately, this exaggerated growth rate didn't last too long. In the past year, while Hibari's life force continued to slowly increase due to these stimuli, his physical appearance hadn't changed much, or rather, had basically stopped changing altogether.
This also put Hibari somewhat at ease. After all, if he had continued growing at that previous pace, he would have had to seriously consider whether to abandon Lightning Release Chakra Mode for the sake of his 'looks.'
After chatting about such topics for a bit, Hashirama then asked with interest, "For these past three years, I've only come back once every month or so, and each time, I couldn't stay for too long, as there are many things in the capital city that require my attention. So, even now, I'm not entirely clear, besides your obvious physical and external growth... has your strength been neglected at all? After all, you, kid, don't seem to have focused solely on that one thing; you even created an impressive Mitsumine Group..."
Hibari grinned, chuckling as he said, "I always remember the teachings of you, Hashirama-jiisan, and Tobirama-jiisan, that strength is the fundamental basis of everything. How could I forget? Don't worry, I've never neglected such matters."
Hashirama listened to Hibari's words, smiled, then stroked his chin, saying noncommittally, "Is that so?"
Hearing Hashirama's somewhat skeptical tone, Tobirama set down his teacup and said, "Whether it's true or false, we'll know after testing him. It's already late today, so let's skip it. But first thing tomorrow morning, why don't we go to the training grounds and test this kid?"
Test...
Hibari hadn't heard this word from his ojiisan in a long time. Ever since Hashirama stepped down and Tobirama took over as the Second Hokage, he had been incredibly busy. His various teachings for Hibari had also slowed down considerably, largely relying on Hibari to learn on his own, and he'd only offer guidance when he had free time to clarify anything Hibari didn't understand.
On the other hand, Hibari, having reaped the benefits of Lightning Release Chakra Mode, would naturally be more attentive to it. He also had to study Hashirama's Wood Release Kekkei Genkai legacy, had some Anbu matters to deal with, and controlled the entire Mitsumine Group.
Even with Hiyoko occasionally helping him with some 'business,' he was still incredibly busy. Therefore, he had indeed fallen behind a lot in his studies with Tobirama, and his progress wasn't significant.
With Hibari himself being so busy, Tobirama, as the Second Hokage, was even busier. Thus, he hadn't tested Hibari in a long time.
Thinking of this, Hibari felt a little excited. He also wanted to know how big the gap in strength still was between him and his ojiisan. Perhaps... he had already become stronger than his ojiisan?
Once his thoughts reached this point, Hibari couldn't hold back. He confidently said, "Alright, tomorrow, I'll give you a good eye-opener and show you Senju Hibari's capabilities!"
He paused for a moment, then Hibari continued, "Of course, for this test, shouldn't we continue our old rules, Ojiisan?"
Tobirama chuckled when he heard Hibari's words and said, "What are you eyeing now, kid?"
"What do you mean 'now'? I said years ago that it's about time you taught me the Yin Seal! And that Flying Raijin Technique of yours! Oh, and I'm very interested in that jutsu you've recently researched concerning the dead. You should teach me all of these now, right?" Hibari quickly said with dissatisfaction.
Tobirama's expression changed when he heard Hibari's words. He then said, "How did you know I was researching that jutsu involving the undying? I haven't told you anything about that jutsu..."
"Ojiisan, I'm not who I used to be. The barrier you set up at your lab entrance, after my long-term study, was already deciphered half a year ago. I've already snuck in many times, alright?" Hibari said smugly.
Tobirama didn't know what expression to make when he heard Hibari's words. Actually, the barrier he set up, while not simple, certainly wasn't overly complex. After all, his laboratory was within Konohagakure, then within the Senju clan's main residence, so one more layer of comparable security was enough; generally, no accidents would occur.
But no matter how well you guard against outsiders, it's hard to guard against an inside job. No matter how complex the barrier, it couldn't stand up to Hibari constantly pondering and studying it when he had nothing else to do.
After a long time, Hibari naturally figured it out and deciphered it, without even triggering the 'sensor' that would notify him. Hibari had infiltrated it several times silently.
Thinking of this, Tobirama gave a helpless smile and said, "You damn brat, you'll really kill me with anger one day, won't you?"
He paused slightly, and didn't continue to scold Hibari. After all, Hibari had achieved this through his own skill, hadn't he?
Tobirama slightly relaxed his emotions, then said, "As for the Yin Seal, since you've already been able to bypass my barrier without me discovering it, it means your accumulated knowledge in Sealing Jutsu and Barrier Ninjutsu is already quite good. You haven't completely wasted these past three years; you've certainly learned a lot of knowledge..."
At this point, Tobirama turned his gaze to Mito, then smiled and said, "Therefore... Aneja, you once told me to set a standard for Hibari, and only when he met it could he learn this from you... As of now, I acknowledge that he meets the standard."
Mito wasn't surprised when she heard Tobiramau's words. Instead, she smiled and said, "I thought you all had forgotten about this..."
"How could we forget about such a good thing, Mito-baasan? Now I can finally be taught the S-rank Yin Seal! Since I can be given this S-rank Sealing Jutsu, does that mean I can also learn many other Sealing Jutsu from you later?" Hibari asked excitedly.
Mito looked at Hibari's eager expression, and finally nodded, saying, "If there's anything you want to learn, just come find me. I'll teach you."
Then Hibari thanked her very happily again, saying he would buy many good things to show filial respect to Mito, making her quite pleased.
After some playful banter, Tobirama, seeing that the matter was more or less settled, continued, "The Yin Seal matter is decided. You can go learn it from Mito-aneja later..."
"What about Flying Raijin?" Hibari asked, raising an eyebrow.
Tobirama looked at Hibari's expectant gaze, and finally smiled, saying, "Flying Raijin... The prerequisite for learning this jutsu depends on whether you can perfectly demonstrate it to my satisfaction in tomorrow's test."
"What prerequisite? If you're talking about accumulated knowledge in space, I think I already meet the standard! At worst, Ojiisan, you can give me a written exam..." Hibari quickly said.
"If Flying Raijin was purely about space, it would just be called a Space Ninjutsu. Why call it a 'Space-Time Ninjutsu'?" Tobirama said with a smile.
Then, without waiting for Hibari to continue asking, he no longer concealed anything and said directly, "Of course, this 'time' doesn't require you to delve into the temporal system; that's something to learn in Genjutsu. The 'time' I'm referring to is something that acts upon oneself. I didn't classify Flying Raijin as a kinjutsu, so theoretically, anyone can learn this jutsu. But the problem is that one's physical qualities must keep up! You must be able to adapt to extremely rapid space-time changes!"
"My physical qualities can't keep up? Ojiisan, can you find anyone in Konohagakure healthier than me?" Hibari asked, raising an eyebrow.
"Who said anything about that? I'm talking about nerve reaction speed. You certainly weren't up to standard before. The Flying Raijin Technique is too fast. If your reaction speed isn't up to par, then learning this jutsu is a death wish. But then again, if your body's nerve reactions aren't up to par, you won't be able to learn this jutsu either. I specifically set this 'threshold' in this jutsu..." Tobirama said, glaring at Hibari.
Indeed, with Flying Raijin, if one's physical reaction speed can't keep up, it would be, as Tobirama said, a 'death wish.' Changes in space-time will inevitably alter the environment around the body in a sudden instant. This reaction speed determines whether you can keep up with such changes. If not, many problems will arise, such as a physical imbalance.
What if you wanted to land on your feet but ended up landing on your head and dying instantly?
What if you wanted to turn sideways to dodge an enemy's sharp weapon and launch a counterattack, but ended up crashing into it?
Considering all these factors, Tobirama specifically set a 'threshold' in this jutsu. If one's qualities didn't meet the standard and couldn't pass this threshold, then naturally, they couldn't learn this jutsu.
This was just one aspect. Simply put, one's body must be able to keep up with such rapid changes, otherwise, they shouldn't learn it.
In Tobirama's eyes before, Hibari didn't meet this standard. After all, this wasn't measured by strength. Speaking of strength, Hashirama's power was unparalleled in the world, yet he couldn't learn Flying Raijin Technique. Decades later, with talent emerging throughout Konohagakure, only the Fourth Hokage, Minato Namikaze, was qualified to learn this Flying Raijin Technique.
It's clear how demanding the standards for this jutsu were, and how high the threshold was.
But now it was different. Tobirama hadn't tested Hibari in a long time, but just now, he heard Hibari say that the Lightning Release Chakra Mode had significantly enhanced his body's reaction speed.
How much that 'significantly' was, and whether it was enough to meet the standard for learning Flying Raijin Technique, Tobirama wasn't entirely sure right now. That's why he said he'd have to see Hibari's performance during tomorrow's test.
If Hibari met the standard for learning Flying Raijin Technique then, Tobirama, as Hibari's grandfather, would naturally not hide anything in that regard!
After this explanation, Hibari also understood his grandfather's meaning, so he didn't object. He just planned to give him a good show tomorrow and convince him to wholeheartedly teach him the Flying Raijin Technique.
Only after this matter passed did Tobiramau's expression become more serious. He then said, "As for that jutsu concerning the dead..."
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