But Katsuro had an idea.
"Iryo Ninjutsu?" Granny Mito was surprised.
"Yep - it would be obviously useful in battle, and that way, the village will stop thinking I'm a useless freeloader if I work in the hospital."
"Hm. I suppose you could be right," she admitted. Katsuro grinned - that was Granny's way of saying to do it.
"Besides, Granny," he started, "someone needs to look after you when you're old and senile!"
Before she could get her first hit in, Katsuro jumped away.
"Brat, come back here right now!"
Despite his usual prowess, Katsuro found himself humbled by the complexity of medical Ninjutsu. Unlike offensive Jutsu (or even physical training), Iryo Ninjutsu required a deep, intimate understanding of human anatomy, biology, and the delicate art of channeling chakra with such precision that even the slightest mistake could cause harm instead of healing.
Still, he pushed forward.
Tsunade, now 17, was shocked to find him studying her field.
"You? Iryo Ninjutsu?" she asked, half-mocking, half-genuinely surprised. "Did Grandma tell you to learn this?"
"No," Katsuro replied calmly, "I decided on my own..."
She studied him for a moment, then asked, "Why?"
Katsuro looked at her, serious and unwavering. "Because I can't afford to lose anyone else."
Tsunade paused, her usual sharp tongue softened. For the first time in a while, she saw not the genius child prodigy, but someone broken and still hurting, very much like she still was.
"Alright," she said, tossing him a scroll. "Then try this. Let's see how serious you are."
From then on, Tsunade began guiding Katsuro. Teaching him the vital Jutsu such as the Mystical Palm Jutsu and Chakra Scalpel which had the added benefit of improving his stagnating chakra control. Despite her outward teasing and occasional jabs, she recognized the brilliance in him - not just in strength or intellect, but in heart. A heart hardened by tragedy, yet softened by love and loyalty.
One evening, after another long day of training, Katsuro sat on the edge of the Senju compound roof, resting, watching the sunset.
The Princess of the Senju clan sat next to him, and Katsuro absent-mindedly noticed she was sipping from a bottle of sake, despite being underage. "You know," she started, "you remind me of Grandpa."
Katsuro looked at Tsunade. "Hashirama-sama?"
She nodded. "He was crazy strong. But he also had a lot of burdens, and wanted to change the Shinobi world."
"I want to become like him, the God of Shinobi," he replied. "I want my name alone to scare people from acting against my loved ones." He said with conviction.
She rolled her eyes but gave him a small smile.
Before their usual sessions in the evening, Katsuro was expecting Tsunade with fish in hand. But was surprised to see a guest he had not seen in a while, her little brother, Senju Nawaki. The little brat would always pick a fight with him for apparently stealing his sister - that, or not being a ninja.
"Tsunade, why have you brought the little sapling?"
"Katsuro! I will finally defeat you and stop you from corrupting my sister!"
Tsunade bonked his head, "Shut up, Nawaki."
I guess this is how Tsunade must have felt when she first met me.
"Katsuro, don't ignore me! Let's fight!"
Despite his grievances, Katsuro didn't dislike the kid, and would indulge his whims. In fact, in all honesty, he saw him as a little brother who had lost a parent, just like he had.
And besides, being raised by Tsunade must have been hard enough.
"I will show you! I will be Hokage, Katsuro!!"
Katsuro chuckled as they began their spar as Tsunade watched on fondly. Nawaki was only 8 while Katsuro turned 13 not too long ago, and unlike Katsuro, he was not a prodigy. But he was making progress - their spars often involved Katsuro subtly teaching and handing advice to Nawaki, in the hopes that he would become stronger, and be able to face the dangers of being a shinobi.
For the next few years, Katsuro continued his training while his spars with Nawaki became more frequent and formal, acting as an older brother and teacher for the young Senju. But Katsuro also started working at the Konoha hospital alongside Tsunade, becoming one of their most valuable practitioners. Having saved countless villagers and shinobi from injury and death, he not only hardened his mentality and improved his skills, but earned the gratefulness and respect of the village that had previously shunned him. Somewhat surprisingly, the hospital noted a rise in small injuries among female villagers and shinobi requesting Katsuro. Unfortunately, contrary to what one might believe, this was not good for him, and more often than not led to Tsunade becoming increasingly irritable and hitting him due to his inflated ego. It only became worse as Katsuro became older, at 17 he stood at 6 feet tall with his white hair long tied in a ponytail, sword-like eyebrows, sculpted jaw and piercing green eyes that more and more girls seemed to get lost in. The more handsome he got, the more annoying Tsunade found him.
Sigh. "It is a curse to be this handsome…" he would say, to which Tsunade would have ticks on her forehead and punch him through a wall. Even Sakumo, who was now more familiar with the Senju family, would join in on complaining about the growing ego his disciple had. But strength wise, Katsuro had grown to the point where Sakumo could not beat him, he had adapted and used his techniques to suit himself switching from a short sword to a Katana made of chakra metal while also using Sakumo's shunpo and his expertise in Lightning nature transformation to create Lightning Style: Thunderclap Impulse, which enhanced the parameters of one's body, particularly their speed and reaction time immensely. This Jutsu used lightning to stimulate the body's nerves and muscles and was inherently very dangerous requiring immense control, expertise and body strength to withstand it. The development of the Jutsu would not have been possible if Katsuro did not know Iryo Ninjutsu, requiring constant trial and error with numerous injuries.
But despite the struggles of watching his disciple harm himself, Sakumo was grateful having been taught it by Katsuro which led to a considerable enhancement in his strength. Sakumo was sure Katsuro was holding back in their spars a lot, focusing only on his Kenjutsu often. In a life or death battle, his chakra capacity alone would be reason for Sakumo to fear him, but his genius in Ninjutsu creation was terrifying. Sakumo had witnessed him create all manners of Jutsu from improving his 'Chidori' to be able to elongate and create needles and combine with his sword, to a fire style Jutsu that would create 9 flame dragons which was akin to an S rank Jutsu! And he was sure his disciple had many more cards up his sleeve.
"Sensei, are you ready?" Katsuro asked unsheathing his katana.
Katsuro's words took Sakumo out of his own thoughts.
"Of course," he replied.
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