Naruto: Aizen's Shadow in Konoha

Under the sales of medical scrolls, a portion of the profits was distributed to the medical ninjas who contributed to their creation, while the remaining funds were directed to the Medical Corps' finances. These funds were used to support the training of new medical ninjas and to further develop the department.

Despite their critical role in improving the survivability of combat squads, medical ninjas often faced two glaring weaknesses:

Limited Combat Abilities: While invaluable in healing and support, most medical ninjas lacked combat prowess, often requiring protection from their squadmates. This indirectly weakened the squad's overall combat effectiveness.

Vulnerability in Combat: Medical ninjas were typically unfit to handle sudden threats, making their survival a significant concern during missions.

To resolve these issues, Aizen implemented two revolutionary changes.

Aizen, drawing inspiration from the Shunpo technique in the Bleach universe and combining it with Konoha's Body Flicker Technique, developed a new mobility-focused jutsu tailored for medical ninjas. He called this technique "Shaved".

While slightly slower than the Body Flicker Technique, Shaved required no hand seals and was significantly easier to learn, making it ideal for widespread use among medical ninjas.

This technique drastically improved the ability of medical ninjas to evade enemy attacks and reposition themselves effectively on the battlefield.

Aizen recognized that teaching medical ninjas advanced combat ninjutsu would demand too much time and energy, potentially detracting from their focus on healing arts. Instead, he addressed their combat role through enhanced perception abilities.

Building upon the principles of spiritual perception in the Bleach universe, Aizen developed a simplified version of Spiritual Perception, specifically tailored for the medical ninjas of Konoha.

This version allowed users to sense chakra signatures within a one-kilometer radius. However, its complexity meant only a select few, typically sub-commanders, could master it.

Aizen then created a more accessible version, halving the perception range to 500 meters. Despite its reduced complexity, it was still beyond the reach of many medical ninjas.

After additional modifications, Aizen developed a final version with a perception range of 300 meters, drastically reducing the learning difficulty. This version, while limited, became widely adopted across the Medical Corps.

To standardize its use, Aizen classified the technique into three tiers:

Primary: Basic version with a 300-meter range, suitable for most medical ninjas.

Intermediate: Moderate difficulty with a 500-meter range, for team leaders.

Advanced: A challenging variant with a one-kilometer range, reserved for sub-commanders and above.

The success of Aizen's reforms, particularly the implementation of Spiritual Perception, caught the attention of Hiruzen himself. The Hokage personally visited the Medical Corps to observe its integration and praised Aizen for his ingenuity

It's worth noting that medical ninjas, as a masters of chakra control, are among the most skilled in manipulating their chakra. This talent made them uniquely suited to mastering techniques like Shaved and Spiritual Perception, further enhancing their value to the village.

Ordinary ninjas couldn't learn these techniques at all.

This highlighted the importance of natural talent in ninjutsu.

Both Shaved and Spiritual Perception were specifically developed to leverage the exceptional chakra control abilities unique to medical ninjas. Without such refined control, no other ninja could master these techniques effectively.

With the implementation of Shaved and Spiritual Perception, medical ninjas became indispensable in combat squads. These techniques granted them survivability, perceptive capabilities, and the ability to heal their comrades—qualities no combat team could afford to pass up.

This surge in demand not only enhanced the value of medical ninjas but also elevated the importance of the Medical Corps within Konoha. Once considered primarily a logistics department, the Medical Corps was now a strategic powerhouse.

Previously, while the Medical Corps was vital, it was largely viewed as a support unit. No one dared offend it, knowing that medical assistance was essential in times of need. However, with Aizen's reforms, the rapid expansion of the Medical Corps' staff ensured broader coverage in both support and combat roles and the introduction of medical scrolls as crucial tools gave the Medical Corps control over valuable resources. 

These changes made the Medical Corps a decisive factor in Konoha's military strength. For example, during a contentious high-level meeting about Minato's promotion, Aizen's support for Minato forced hesitant senior leaders to approve the decision.

Why? Because offending Aizen now meant being blacklisted by the Medical Corps:

They wouldn't have access to medical scrolls and their teams would be excluded from receiving medical ninja support.

This would drastically increase casualties within their clans, putting them at a disadvantage against other families that maintained good relations with Aizen and the Medical Corps.

Tsunade, long disinterested in actively managing the Medical Corps, heard of Aizen's reforms and achievements while living outside the village. Recognizing his talent and dedication, she formally submitted her resignation as Head of the Medical Department to Hiruzen, fully endorsing Aizen as her successor.

This transition happened seamlessly, and Aizen's promotion to Head of the Medical Department was quickly finalized. Shortly after, he was also appointed as a Vice-Captain of the Shinobi Division, overseeing 2,000 ninjas.

At the same time, Namikaze Minato was also being considered for a significant leadership position in the Shinobi Division. With his Kage-level potential, his role as Anbu's Vice-Captain, and his growing reputation, he was poised to manage a force of 5,000 shinobi.

However, this proposal faced heavy resistance from Konoha's senior leaders. A force of 5,000 was a significant share of Konoha's overall military strength, and many feared such power concentrated under Minato.

It was Aizen's decisive intervention during the meeting that secured Minato's appointment.

Jiraiya, recently returned to the village, also spoke on behalf of Minato during the meeting. Unfortunately, his efforts only seemed to intensify the resistance from the opposing senior leaders.

Watching Aizen effortlessly command attention and sway the meeting's outcome, Jiraiya couldn't help but feel a pang of disbelief. He reflected on how far Aizen had come—from being a young ninja attending high-level meetings as a bodyguard during the Second Shinobi World War to now wielding immense influence within Konoha.

In just a few short years, the once-youthful and unassuming ninja had grown into a formidable leader.