Sasuke's expression froze instantly, his face twisting slightly. He seemed to want to open his mouth, but an invisible force was struggling within him.
"Just messing with you!" Shinsei laughed. "I'll teach you. Stop looking so stiff all day!"
"I have some ideas about Lightning Release, too. I can teach you," Shinsei said seriously. "But your problem isn't just ninjutsu. Your foundations are too weak."
Much better than Naruto's, of course, Shinsei added inwardly. But Naruto would soon have Jiraiya teaching him, so he didn't need to worry about that. If he stopped Sasuke from going to Orochimaru, then naturally, he would have to provide comparable instruction.
His earlier claim that Kakashi could teach Sasuke wasn't empty talk, but there wasn't much left Kakashi could teach him. Experience aside, Kakashi himself lacked powerful ninjutsu, though that had something to do with his low chakra reserves and his not having developed large-scale ninjutsu.
He also wanted to know who would be stronger: himself, a transmigrator, or the Sasuke Uchiha trained by Orochimaru.
He wasn't afraid of Sasuke surpassing him if he taught him, either. As a transmigrator with the Senju bloodline, if a native surpassed him, he might as well give up.
"Hold out your hand."
Sasuke obediently extended his right hand. Shinsei took it in his left, and a faint spark of electricity flashed.
A wave of paralysis left Sasuke unable to move. He tried to gather chakra to fight back, only for it to be easily dispersed.
"How does it feel?"
Sasuke knew Shinsei wasn't bullying him for no reason, so he answered honestly, "My whole body's numb. I can't muster any chakra."
"You know about chakra properties, right?"
"Yes."
"What properties does lightning release chakra have?"
"Paralysis." Sasuke then recalled his Chidori. "Penetration."
Shinsei nodded, walked aside, and casually sliced off a piece of wood with Lightning Sword. He returned and sat beside Sasuke, gripping the wood in his right hand. Electricity crackled wildly, gradually charring the damp wood.
Sasuke stared, dumbfounded. This had caught him by surprise. As someone who also possessed the Lightning Release affinity, he naturally knew how difficult this seemingly casual feat was.
"And burning!" Shinsei tossed the wood aside. "You have Fire Style chakra, so you can do this easily, too."
That's hardly easy, Sasuke thought. Being able to do that would mean having a new ninjutsu that needs no hand seals.
"Here's some homework." Shinsei picked up a fresh piece of wood. Electricity flashed over his hand, and lightning release chakra burned the characters for "Shinsei" into the wood. "Practice this at home. It's a prerequisite for Lightning Sword, a ninjutsu that needs no hand seals."
Shinsei had previously used this method to practice the properties of lightning release chakra and his control. Now he was teaching it to Sasuke, too.
Sasuke took the wood from Shinsei and stared blankly at the lettering burned into it by lightning release chakra. How could that even be done?
Shinsei raised his eyebrows. He wasn't exactly lying, though practicing Lightning Sword didn't require such advanced chakra control. Still, he had to give Sasuke a more distant goal. Without a few tricks up his sleeve as a teacher, his student wouldn't be so obedient.
It would naturally be even better if Sasuke really managed it. His ninjutsu without hand seals was far stronger than Sasuke's Chidori Stream in the original story. Ever since developing it, he had yet to encounter anything it couldn't cut through.
"Don't move!" Shinsei reached toward Sasuke's neck.
Sasuke stopped the hand he had been about to raise to block him and placed it on his knee.
A trace of chakra emerged from Shinsei's fingertip, lightly touching the Cursed Seal on Sasuke's neck. Through his fingertip, he sensed dark, evil chakra entrenched within the Cursed Seal.
This chakra was unfamiliar. Shinsei had never encountered anything like it. There also seemed to be another kind of energy continuously gathering and then being stored. According to the original story, the Cursed Seal was the product of Orochimaru's research into senjutsu. Was this unfamiliar energy natural energy, then?
"Can you activate it briefly? Just a moment will do." Shinsei looked at Sasuke. Every activation of the Cursed Seal seemed to harm Sasuke in his current state, so he couldn't force him.
Sasuke said nothing, but the Cursed Seal on his neck began to rotate before rapidly spreading over his entire body.
Evil, violent chakra struck back through Shinsei's fingertip, seemingly trying to invade him in turn.
"That's enough."
At Shinsei's words, Sasuke immediately collapsed to the ground. Activating the Cursed Seal twice in a row was a considerable burden for him, too.
"I have a rough theory." Shinsei gathered his words. "There are two types of chakra mixed inside. This is a ninjutsu created by incorporating sealing jutsu. Its purpose is to store a special kind of energy that exists between heaven and earth."
"What special energy?" Sasuke looked puzzled. He only knew that chakra was physical energy and spiritual energy.
"Uh... natural energy. You don't need to know so much right now. What you need to do now is strengthen your body so it can adapt to the Cursed Seal." Shinsei couldn't easily explain where he had learned about natural energy, though fortunately, the Senju also had access to senjutsu. Explaining this sort of thing would only lead to more and more complications.
"All right! That's it for today!" Shinsei hurriedly cut off Sasuke's further questions. He hadn't even practiced the new ninjutsu he had obtained yet.
Sasuke really does have a pretty good temperament. Naruto would definitely keep pestering me.
Mount Myōboku.
An enormous orange toad, its skin covered in wrinkles, sat in a huge stone chair, sleeping with its eyes closed.
Suddenly, the old toad opened its eyes, which seemed filled with fear.
"Ribbit~"
The toad's call carried far into the distance.
A humanoid toad wearing an apron and holding a spatula hurried into the hall.
"You're awake, Great Sage? Fukasaku went out to gather bugs. I was just cooking." The small humanoid toad wiped her hands back and forth on her apron.
"Shima, bring Jiraiya here!"
"Have you had a new prophecy, Great Sage?" The humanoid toad Shima thought little of it. The great toad before her had already grown senile and often spoke incoherently after waking.
"I saw a new dream!" The Great Toad Sage nodded his head.
"What did you dream about, Great Sage?" Shima wanted to ask exactly what the dream was, or she wouldn't be able to answer any of Jiraiya's questions.
Inhale... exhale... inhale... exhale...
The great toad's even breathing gradually turned into snores.
He really has gone senile, Shima grumbled inwardly. Still, she had to go fetch Jiraiya.
In Konoha, a white-haired, middle-aged man crouched at a window, furtively peering inside. A faint haze of steam hung before the window.
The white-haired, middle-aged man drooled, a silly grin covering his face.
Naruto watched the white-haired man ahead of him peeping through the window.
"Hey! Are you peeping?" Naruto pointed at the man before him and shouted.
"Shh!" The white-haired man hurriedly turned around and gestured for silence.
"Who are you? Why are you peeping here?" Naruto ignored the white-haired man's gesture. He only wanted his voice to alert the people bathing inside.
"This isn't peeping! It's research! Research, understand? As for who I am..." The man gesticulated theatrically. "I am Jiraiya, the Toad Sage of Mount Myōboku!"
As he spoke, the man summoned a toad as tall as a person and sat on it.
The orange toad looked around, then glanced upward and spotted Jiraiya.
"Big Brother Jiraiya, Sage Shima was just looking for you! She'll summon you over in a moment."
"Huh? What bad timing! I'm in the middle of research!" Looking rather reluctant, Jiraiya pointed at Naruto, who was watching the show in front of him. "Don't you go anywhere, brat! I'll settle the score with you later for interfering with my grand research plans!"
"I'm not scared of you! You peeping old man!" Naruto yelled.
"Someone's peeping!"
"Catch the pervert! Don't let him get away!"
Bang!
A cloud of white smoke burst out, and Jiraiya vanished along with the toad, leaving Naruto standing there, scratching his head in a daze.
"Brat! Were you the one peeping?"
"It wasn't me! It was a white-haired old man!"
"Then where is he?"