After Mizuki returned home, Haruki once again found himself a regular guest at her house, happily enjoying her cooking. But more than just meals, Mizuki had also taken it upon herself to personally train Haruki—teaching him the secrets of the Hyūga clan's Gentle Fist and the proper use of the Byakugan.
Haruki, who was well-versed in the history of the shinobi world, knew full well what the Byakugan represented. It was the Kekkei Genkai of the Hyūga clan, a power inherited from the legendary Ōtsutsuki Kaguya, the progenitor of chakra. Her younger son, Ōtsutsuki Hamura, inherited her Byakugan and later led his clan to the moon. The Hyūga were the descendants of those who remained behind on Earth—heirs to Hamura's celestial eyes, though not his divine body.
The Byakugan was an extraordinary dōjutsu. It granted vision extending over a kilometer and offered nearly complete 360-degree perception. Main branch members of the Hyūga clan could see the full range around them, while branch family members, due to the Caged Bird Seal, had a single blind spot—about one degree directly behind the first thoracic vertebra.
Its x-ray-like perception allowed users to see the chakra network within a person, observe chakra flow in real time, and even gauge the nature and origin of a target's chakra. Skilled users could detect illusions, anticipate ninjutsu, and recognize individuals by their chakra signature alone.
Another unique trait of the Byakugan was how easily it could be awakened. Unlike the Sharingan, any Hyūga-born shinobi could activate it. More impressively, those with the Byakugan could emit chakra from any tenketsu point on their body—something no ordinary ninja could do.
Of course, these advantages primarily applied against average shinobi. The Byakugan wasn't omnipotent. It couldn't compete with every elite technique. Haruki had studied well and knew the strengths of other villages—Kirigakure's Water Release, Konohagakure's Fire Release, Kumogakure's Lightning Release, Iwagakure's Earth Release, Sunagakure's Wind Release—plus countless other Kekkei Genkai and forbidden jutsu. In most modern squads, Hyūga shinobi were assigned reconnaissance or battlefield surveillance roles rather than direct combat leadership.
"Haruki, to activate the Byakugan, you need to guide your chakra through the network to your eyes—like this."Mizuki formed a series of hand seals in front of her chest and then called out,"Byakugan!"
A burst of pressure erupted from her brow. Her pupils turned pale blue-white, veins bulged around her temples, and her irises shifted into concentric patterns—her gaze sharpened, piercing through everything around her.
"Still looks like cataracts," Haruki mused to himself.
Mizuki let the chakra fade. Her eyes returned to normal as she smiled, continuing her explanation.
"Once you've mastered it, you won't even need to form hand seals. Like this."Without forming a single seal, the veins around her temples bulged again, and her Byakugan reactivated instantly.
She then walked Haruki through the sealing sequence, how to route chakra from the dantian through the chakra network to the eyes, how much chakra to use, and which flow patterns to follow. Haruki listened carefully and began practicing.
"Byakugan!"
As soon as the chakra reached his eyes, Haruki felt the veins around his temples throb and tighten. A surge of perception overwhelmed him. The world transformed—black and white, yet vividly detailed. He could see behind himself without turning. Mizuki's chakra system lit up clearly within her body. Even the plants behind her shimmered with detail. His gaze pierced the trees ahead as if they were made of glass.
He was amazed.
Within a 100-meter radius, everything was crystal clear. The rustle of leaves, the sway of blades of grass—nothing escaped his vision. When he focused, he could even make out the bark patterns on a distant tree as though he were standing right next to it. But beyond that range, the clarity began to blur. Around 500 meters, the precision faded into normal vision.
"So my effective range is 100 meters," Haruki thought. "I can push to 500, but only with diminished clarity. It's like having a 100-meter x-ray and a 500-meter telescope. I'll need to keep training. One day, I want to see far beyond even that."
Excited, he wondered,"Let's see if I can activate it without using seals. My chakra control training should help."
Deactivating the Byakugan, Haruki calmly focused. He slowly guided his chakra to his eyes—no hand seals. The veins pulsed again, and the Byakugan flared to life.
"Haruki... you activated it without seals?" Mizuki's eyes widened.
"Yeah, Mizuki-nee. It was a bit hard, but I managed," he replied with a sheepish grin.
"Most people need months to reach that point," she said, blinking in disbelief. "It took me half a year to activate the Byakugan without hand seals... Are you some kind of prodigy?"
"Haha, I don't think so... I've just trained my chakra control a lot," he said, scratching the back of his head.
Just then, Haruki's vision returned to normal—his Byakugan had deactivated on its own.
"Huh?" he blinked. "What happened?"
He glanced inward and realized his chakra was nearly depleted.
"What the... I only used the Byakugan for five minutes! Why did I run out so fast? How do Neji and Hinata maintain it during battles? I thought the chakra cost was supposed to be low!"
Mizuki noticed his puzzled expression."Getting the hang of it?" she asked.
"Mizuki-nee... is the Byakugan supposed to burn through this much chakra?"
She shook her head. "Not at all. The chakra consumption is minimal. Even a Genin can keep it active for at least an hour. Chūnin can go for four or five hours without issue. Jōnin often keep it active during missions for constant scanning."
"Then why am I drained after just five minutes?" Haruki asked, frustrated.
"Maybe you're overcharging it," Mizuki suggested. "Try activating it again. I'll observe your chakra flow."
Haruki waited until his reserves recovered by about two-thirds, then activated the Byakugan again.
Mizuki watched closely, thoughtful. Within minutes, Haruki's chakra was depleted again.
"You're controlling the flow perfectly. The amount is fine," she muttered, puzzled. "But your eyes are absorbing it way too fast... like they're consuming chakra at an insane rate."
"So what's going on?" Haruki groaned.
"I've never seen this before... but I have heard of something similar," Mizuki said slowly. "The Hyūga main family's bloodline is far purer than the branch family's. Their Byakugan is sometimes called the 'Pure Eye.' Long ago, they were even referred to as princes or princesses of the Byakugan. Their eyes are far more efficient—stronger vision, lower chakra use."
"But your chakra loss is extreme," she continued. "It's beyond even what I've read about."
"Pure Byakugan... That's right," Haruki murmured. "Ōtsutsuki Toneri once called Hinata a princess of the Byakugan. Because of her pure bloodline..."
"Could it be," he thought, "that my Byakugan is the opposite? An unstable or impure version?"
After a short rest, Haruki activated his Byakugan once more. This time, he turned his gaze inward, tracking the chakra flow from his dantian to his eyes.
The flow was rapid—so rapid, it was almost violent. The moment chakra reached his eyes, it was devoured. The Byakugan felt like a ravenous beast, constantly demanding more.
He glanced at Mizuki. Her chakra flow was steady, gentle.
Then he looked back at his own. The contrast was stark. He compared every detail—his Byakugan structure, chakra pathways, pressure points, and lower abdomen network. He combed through his entire system.
And then, he saw it.
"What the...?!"
Haruki's heart skipped a beat.