Curtain Call
The reason Shirō delved so deeply into this research wasn't only to better understand his own situation, but also because of his ambition.
After being modified by the system, Shirō's body possessed twenty-seven magic circuits—the same number as Emiya Shirou from the Fate series. However, unlike Shirou, Shirō's body still contained Chakra Pathways that hadn't been converted into circuits. If he could fully master the technique of bridging chakra and magecraft, it would bring him tremendous benefits.
Yet, despite countless attempts, Shirō's experiments had yielded no breakthroughs. Every trial so far had ended in failure. Still, it wasn't all wasted effort: his failures had at least deepened his familiarity with magecraft theory and practical use.
The main obstacle wasn't only his limited understanding of magecraft, but also his refusal to perform human experimentation. Shirō understood clearly: killing on the battlefield and dissecting innocents in a lab were two very different matters. Besides, his current workshop's security was weak. Conducting human experiments here would be suicidal—he wasn't foolish enough to take that risk.
That said, he had a strong premonition that Katsuki's mutation would be the key to a major breakthrough. For now, though, he restricted himself to analyzing Katsuki's cells through magecraft, avoiding anything extreme.
Since returning home, aside from greeting Keiko and the others, Shirō had locked himself in the laboratory, tirelessly testing how Katsuki's cells would respond under sealing techniques. The operation to stabilize her was scheduled for that evening, and the more he understood, the safer she would be. Compared to Katsuki's situation, Shirō's personal ambitions could wait.
His twenty-seven circuits improved his efficiency at refining chakra, but not the actual amount of energy available. After all, modern magecraft didn't allow him to tap into the natural world's mana like a true magus of the Fate world.
By late afternoon, he had finished testing every sealing array that Uzumaki Kushina had prepared. As expected of a member of the Uzumaki clan, Kushina's fuinjutsu was formidable—far beyond what most Konoha shinobi could hope to match. The results were reassuring: Katsuki's cells responded normally to the seals, though he admitted the observation window was short. For now, controlling the mutation was more important than understanding it fully.
Interestingly, his analysis showed that Katsuki's mutated chakra pathways resembled magic circuits, but the similarity was only superficial. If they truly were circuits, Katsuki might be able to study magecraft with him. But if not, forcing it could cripple her completely. Worse, if Minato's suspicions were correct, transforming her pathways into circuits might strip Katsuki of her innate gifts: the Kagura's Mind Eye and the Adamantine Sealing Chains—a disaster for an Uzumaki.
Because of this, everyone, including Kushina and Minato, agreed that the safest course was to seal the mutation for now and attempt permanent removal later.
At Kushina's home, Shirō and Minato waited in the living room while Kushina worked. Since the procedure required physical contact, it wasn't proper for them to assist. Minato, however, had already marked the room with Flying Thunder God in case something went wrong, allowing him to intervene instantly.
Fortunately, Kushina's fuinjutsu had no mere reputation—the sealing went smoothly. Katsuki's mutated pathways were suppressed, though she would need two days of observation before she could even attempt ninjutsu again. In the meantime, Kushina decided to drill her in fundamentals: hand seals, taijutsu basics, and sealing theory. A shinobi's strength wasn't limited to flashy ninjutsu, after all.
By the time it was finished, night had already fallen. To save time, Minato simply transported Shirō home with Flying Thunder God.
"Well then, Shirō. See you tomorrow."
"Yeah. See you."
With a whoosh, Minato vanished.
Shirō exhaled softly, a hint of envy flickering in his eyes. That jutsu was far too convenient. He had once tried to train in it himself, but lacking Minato's extraordinary space-time affinity, he'd failed completely. With a shake of his head, he pushed the thought aside, quietly opened his door, and stepped inside.
Keiko and the others were already asleep, so he moved silently, setting up a soundproof barrier around his room before tending to his half-healed wounds. Years of experience with injury had allowed him to refine his medicines, and he estimated that two more treatments would fully restore him.
Once finished, he pulled out a magecraft scroll and resumed his studies. The last mission had reminded him sharply of his limits. While he could now defeat a Jōnin-level opponent in an instant when fighting seriously, that was only against someone unfamiliar with his abilities. His Noble Phantasms gave him an overwhelming advantage in surprise, but against a well-prepared enemy? The situation would be different.
And ultimately, Jōnin were still only mid-tier in the shinobi world. In future wars where Kage, tailed beasts, and even gods moved, Jōnin would be mere cannon fodder.
Konoha boasted no shortage of such elites. Official records listed over a hundred Jōnin in its mission-active roster alone—the highest among the Five Great Nations. Beyond that, powerful clans like the Uchiha also had their own internal Jōnin, many of whom weren't counted in official numbers. Add in the ANBU, the Special Jōnin, and Danzō's Root, and the village's true combat strength reached well over a thousand.
A daunting thought. And one more reason Shirō knew he couldn't afford to stagnate.
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