In the end, Seisuke chose to learn Senjutsu: Hakugeki no Jutsu (White Rage Technique), Senjutsu: Mukyō Tensei (Inorganic Reincarnation), and Senjutsu: Ibutsu Henka (Object Transformation). Both Hakugeki no Jutsu and Mukyō Tensei were later studied by Kabuto Yakushi—proven to be immensely powerful senjutsu.
Hakugeki no Jutsu works by vibrating air in a specific area, causing targets to feel as if their bones are grinding together, leading to numbness. The technique also emits deafening sound and intense light, impairing both hearing and vision. Its terror lies in disrupting even the Susano'o forms of Sasuke and Itachi. Fortunately, Seisuke's sage-mode cornea and elemental transformation ability allowed him to ignore these effects—otherwise, using this technique would harm him as much as the enemy.
Mukyō Tensei is not a simple chakra-controlled material manipulation jutsu. It's a reincarnation technique that imbues inanimate objects with life, allowing users to shape stones, earth, and other inanimate matter at will. Under this technique, inanimate objects move with startling speed.
Ibutsu Henka, a unique genjutsu illusion of Tatenokami Hime, was the technique Seisuke first witnessed when they met—creating magnificent gatehouses and lifelike food that blurred the line between illusion and reality, approaching "true fantasy."
Seisuke prioritized Mukyō Tensei. Hakugeki no Jutsu was too indiscriminate, harming friend and foe alike, usable only in solo missions. Mukyō Tensei, however, suited him perfectly—altering terrain to gain tactical advantage in both offense and defense, offering exceptional cost-effectiveness.
But the learning process...
"Are you even listening?" Ichikishima Hime was explaining Mukyō Tensei's principles and usage, her lengthy lecture driving Seisuke to existential doubt. Who am I? Where am I? What am I doing?
"Pay attention!" Ichikishima Hime pinched his cheek. "Do you know how many people dream of learning senjutsu? Even your teacher never had this chance! Don't take it for granted!"
Throughout history, only four humans (including Seisuke) had learned Ryūchi Cave senjutsu. The last was from who-knows-how-long ago, and Ichikishima Hime's teachings relied on outdated materials, leaving Seisuke confused and overwhelmed.
"I know, I know! I'm processing it! But being human has limits, Ichikishima Hime!" he protested.
"If abandoning humanity would speed up your learning, I'd ask Lady White Snake Sage to turn you into a snake again."
Recalling the previous agony, Seisuke immediately relented: "I'll study hard!"
"Good. Now, continue. When using Mukyō Tensei, pay attention to..."
Back in Konoha for dinner, Seisuke was dazed. Asuma and Kurenai, who had returned to the village, were startled by his vacant expression.
"Seisuke, really? My old man said you went to Ryūchi Cave to train. How'd you end up like this? You've only been training a day, right?" Asuma asked.
"A day?" Seisuke stared wildly. "Do you know what I went through today? Do you?!"
"Seisuke..."
"Seisuke is dead! Standing before you is Asakawa 'Sage' Seisuke, who will master senjutsu—even the Sage of Six Paths can't stop me! That's a promise!"
Kurenai and Asuma exchanged glances. He'd clearly been through hell. Kurenai soothed, "Okay, okay. Sit down and eat first."
"I won't eat or drink! I must learn senjutsu!"
He's completely gone mad!
"No, he's obsessed. To the hospital! Now!" Asuma hoisted Seisuke over his shoulder and raced to the hospital, Kurenai in tow. All the way, Seisuke shouted: "I will succeed!"
Another strange case of social death added to the list...
Ah, my life is filled with regret!
Recovering in the hospital, Seisuke lay in bed, eyes vacant. Ichikishima Hime's cram-style teaching—dumping knowledge and principles—had overloaded him. Though sage mode enhanced his memory and processing, the information flood, combined with lack of rest, left him disoriented. In essence, he was like someone who'd pulled consecutive all-nighters, emotionally unstable.
Waking up, he realized he'd suffered another social death: Asuma carrying him through the streets while he yelled like a patient refusing medication.
Rin, now working at the hospital, entered and sighed at his defeated expression: "Seisuke, don't be like this. The director said you just need rest. A few days of sleep will help."
"Rin, my suffering exceeds yours," he lamented. "Hear what Konoha says about me: 'Orochimaru's deranged disciple.' But Orochimaru is deranged too!!"
(Note: He doesn't deny being deranged.)
Rin maintained a polite smile: "Get more rest. Sleep will help."
"My life is over."
Closing the door, Rin thought: The director was right—he needs rest.
But rest was the last thing on Seisuke's mind. He returned to Ryūchi Cave to train.
A week later, in Ryūchi Cave, Seisuke gazed at a small earthen mound he'd raised. "Yes! I did it!"
Ichikishima Hime commented: "You need more practice, but you've grasped the basics. Not bad."
"Next, I just need to increase senjutsu chakra output." Seisuke channeled more senjutsu chakra into the ground.
"Senjutsu: Mukyō Tensei!"
The earth seemed to gain life. Under his control, countless spikes erupted from the ground, crashing into the cave ceiling. With a roar, stalactites fell.
Ichikishima Hime nodded: "Acceptable. You've learned it. Let Tazunohime teach you Hakugeki no Jutsu. For Ibutsu Henka, you'll need to request Tatenokami Hime's guidance—she's the only one who knows it."
"I don't have much time. I need to go to the battlefield."
Konoha was still at war, and he needed to join the frontlines against Kirigakure.