For two years, the teams gathered at the edge of the Forest of Death to train.
Shikamaru, Shino, and Lee were paired with Gai. Gai improved Shino and Shikamaru's Taijutsu while he and Lee tried their hand at learning the Six Styles; one of the six styles, Tempest Kick, was giving Lee particular trouble.
While Lee could have moved on and tried other ones more suited to him, like Iron Body, He was too stubborn, trying again and again; his physical limitation of not being able to project chakra out of his body was making this technique impossible for him without using the Eight Inner Gates.
Tenten, Kiba, and Ino were paired with Asuma for elemental training: Tenten got lucky in this regard with wind, Kiba got Fire, and Ino got water, each of them starting on their training of cutting a leaf, burning a leaf, and Ino trying to make a dry leaf wet.
Shizune trained Hinata, the girl taking to the basics of medical knowledge like a fish in water, and with Hinata's kind heart and intelligence, it came as no surprise that she took to the subject as she did.
And Kakashi's shadow clone trains Sasuke and Neji; the other Jonin not busy with students take the time to train themselves, the only Jonin doing both at the moment being Gai.
One thing was certain: everyone was improving at a rapid pace. When not doing missions or having their days off, they were training, and with the help of Kakashi's new bath bombs being sold at an apothecary run by the Nara clan. Each time they left to return home, they'd use a portion of their pay to buy the bath bombs, returning each day fresh and ready to start again.
Sakura, with Tsunade, was experiencing much of the same. Between her medical training, Seven Heavenly Breaths training, and Six Styles training, she had to cut back on the hospital shifts, the bath bombs becoming her best friend over the 2 years, as every muscle ached to the point it twitched with every training session with Tsunade. Tsunade herself bought bath bombs for her student and for herself because, despite the effect being minimal for her, it still meant gaining more chakra each time, and the main reason was recovery.
Kakashi, over the two years, was actively inventing, training, and training others alongside his other Jonin colleagues, each Sensei switching students depending on students' desire to learn certain subjects or what the Sensei thought the individual students needed.
Kakashi also secured the Hokage's direct endorsement after creating a prototype Scientific Ninja tool that fires jutsu based on the type loaded into it. Yellow for Lightning, red for Fire, Blue for Water, tan for Earth, and green for Wind.
Kakashi handed that experiment over one month into the training, already starting to invent in another area, mainly the genetic area, snatching up the lowest of the low bandits he could find to experiment on, mainly going after the ones that have done some things worse than killing someone, crimes against Women, and even worse, children.
He had no mercy, experimenting on over twenty bandits before perfecting it on the twenty-first. An experiment using his own blood to create a serum to improve the ones given it, and what a success it was. The academy-level chakra that the bandit had was propelled all the way to the higher levels of Chunin with the serum, but Kakashi also noticed that the bandit's physical attributes received a large boost while his yin received a smaller boost.
In two more months, Kakashi confirmed that the serum had no side effects; the effects on every bandit he tested were the same: a massive leap in chakra capacity, but they also differed. Such as where their chakra naturally aligned. If one bandit naturally favored the Yin side, his Yin would receive the larger boost; if his Yang received it, his Yang would receive the larger boost.
After exercising further caution and spending another month testing everything, Kakashi presented the serum to Tsunade and showed her the bandits, along with the records about them. Their previous chakra levels, chakra natures, physical improvements, and even the horrible crimes they've committed and their victims- Kakashi's genjutsu proving convincing enough for each of them to spill their disgusting crimes.
By month five of the two years, Kakashi had invented the Scientific Ninja Tool and perfected the Serum.
In month six, Tsunade called the Council. She read them Jiraiya's mission report, finally explaining why she had ordered the teams to train so urgently. She then revealed Kakashi's new Serum, detailing how it's stable and how it has affected weak bandits and turned them into Chunin-level threats in physical and chakra levels, and how Kakashi's serum acted as a sort of catalyst for already existing alignments instead of trying to add something new like with the experiments of Hasirama cells.
She laid the vials on the table. She gave the clan heads a direct choice: take the shot to improve their abilities for the coming threat, or refuse it.
With the information presented before them in prepared folders, each clan head read over the lines one by one. All the information about the serum was scrutinized.
Setting down his folder first, Shikaku looked to Kakashi.
"You explained in the notes here that it's typical for the body to run a fever 24 to 42 hours after taking it. What is that dependent on, and why does the body force the ones you've given this to into sleep?"
"The longer your fever runs, the better the result. It depends entirely on you. 24 hours to 42 is my estimate, but none of the bandits slept for more than 10 hours. For any of you with more potential, it could be 24 to 42 hours, in my estimate. As for your other question, your body will naturally force you to sleep as your chakra pathways slowly but surely expand."
Shikaku volunteered to try it first, refusing to let anyone else risk the injection before he did. Tsunade granted the request, and Shikamaru took time off from training to stay close by with his mother. Both of them stayed right by Shikaku's side as Shizune administered the shot, watching his skin flush with the immediate, high fever before he dropped into a deep sleep.
Two days later, Shikaku finally opened his eyes. The fever was gone, but the room felt different. He did not just see the dark corners; he felt them. Every shadow hummed like they were greeting him.
Shikamaru and Yoshino leaned forward, watching him anxiously.
Ignoring the tightness in his limbs, Shikaku swung his legs out of bed. His body felt heavy; he was completely sharp. He looked down at the dark shadow under his bedside table, testing the bizarre new pull in his chakra.
Without a word, Shikaku leaned forward and stepped directly into the darkness with a subconscious injection of chakra.
There was no sound. His body folded into the blackness and vanished right in front of his family. Yoshino gasped, standing up so fast her chair scraped the floor.
A split second later, the shadow cast by a coat rack on the other side of the room rippled. Shikaku stepped out from the wall, normal once more.
"What was that? H-how?!"
Yoshino was both amazed and a little frightened by how her husband seemed to meld in and out of the shadows. Shikamaru just stared, his eyes wide as his mind raced to calculate the chakra mechanics behind what he had just witnessed.
"Calm down, Yoshino."
Shikaku said, his voice calm but impressed.
"It's hard to put into words. Usually, our shadows are just an extension of our body that we use for capture and other purposes. But right now? I feel much more in tune with them."
He stepped back toward the room, his shadow automatically stretching out to connect with the shadow of the doorframe.
"I'm not teleporting."
Shikaku explained, gesturing to the floor.
"My chakra can reach any shadow within my line of sight. Once that connection is made, I can use that path as a physical tunnel. I'm just crossing the shadows my chakra can reach. It's like walking through a door to another room. It's sort of like anchors that I can feel."
Shikaku rubbed his chin; for the first time, he was completely lost on how to describe the bizarre feeling of shadows in the room.
Following him, the other clan heads in the order of Choza, Inoichi, Shibi, and Tsume got the serum as well, each staying asleep with a high fever for more than a day, waking up with changes that they could immediately feel; the less important, but still useful one being their increased chakra reserves, but each had a unique upgrade to their abilities.
(I'll just put them below instead of explaining the same process for each)
1. Choza Akimichi (Massive Yang Boost)
* The Unique Upgrade: Permanent Density Alteration and Skeletal Reinforcement.
* The Effect: The Akimichi Multi-Size Technique usually enlarges the muscles, making them larger yet soft. The serum worked to permanently thicken Choza's bones and compress his muscle fibers into iron-like density. When he grows into a giant, his weight and impact force are quadrupled.
2. Inoichi Yamanaka (Massive Yin Boost)
* The Unique Upgrade: Multi-Threaded Mental Projection and Autonomous Defense.
* The Effect: The Mind Transfer Technique usually leaves the user's physical body completely defenseless and unconscious. The immense Yin boost allows Inoichi's mind to split into separate, fully functional consciousness streams. He can now possess an enemy's mind while his real physical body stays completely awake, moving, and fighting on its own.
3. Shibi Aburame (Balanced Yin/Yang Boost)
* The Unique Upgrade: Shared Sensory Perception and Accelerated Breeding.
* The Effect: Shibi's cells fuse completely with his Kikaichū hive. His bugs now become tougher, breed five times faster, and can absorb some elemental chakra attacks to protect him. Most importantly, Shibi gains shared perception. He can see, hear, and feel everything his bugs perceive in real time, effectively giving him a massive living radar.
4. Tsume Inuzuka (Massive Yang Boost)
* The Unique Upgrade: True Feral Adaptation (Partial Beast Transformation).
* The Effect: The Inuzuka copy beasts, but the Yang boost gives Tsume actual predatory physical traits. She can now manifest razor-sharp chakra claws, night-vision eyes, and a sense of smell that could track much further than before. Her body also gains a healing factor, closing slashes and minor wounds within seconds of taking them.
5. Hiashi Hyūga (Massive Yin Boost)
* The Unique Upgrade: Visual Focal Expansion and Spatial Blind Spot Elimination.
* The Effect: The Byakugan naturally possesses a tiny, absolute blind spot at the back of the neck. The powerful Yin boost floods Hiashi's optic nerves, permanently fixing this flaw. His field of vision becomes a flawless, 360-degree sphere with zero gaps. Furthermore, his visual perception sharpens, allowing him to track invisible or spiritual attacks long before they make physical contact.
After experimenting with their new abilities on their own, the clan heads collectively agreed to let their kids have them as well, all of them taking it and gaining the same abilities as their parents, or a bit better in some cases. (P.S- Neji got it too)
- Sakura and Tenten -
Sakura Haruno (Massive Yin Boost + Deep Reserves)
* The Unique Upgrade: Monumental Chakra Expansion and Pathway Optimization.
* The Effect: Sakura's natural chakra pathways widen into a deep reservoir. Because her chakra control is already flawless, she does not waste a single drop of this newly expanded pool. These newfound reserves allow Sakura to use more jutsu in combination with her medical jutsu and super strength. It also drastically accelerates the speed at which she can store chakra for the seal that she's going to be getting on her forehead.
Tenten (Balanced Yin/Yang Boost + Deep Reserves)
* The Unique Upgrade: Peak Physical Conditioning and Massive Chakra Reserves.
* The Effect: The balanced serum permanently widens Tenten's chakra pathways, granting her a larger chakra pool. Furthermore, the Yang energy deeply infuses her muscles, bones, and nervous system, pushing her physical form to the 1st Gate of Opening level of power without actually opening the gate.
After each of them had the serum, Kakashi gave the last one to Tsunade. Sasuke didn't really want it, and Kakashi respected that, ending up giving it to Lee.
Rock Lee (Massive Yang Boost)
* The Unique Upgrade: Fixed Chakra Pathways and Physical Repair.
* The Effect: Because Lee could not push chakra outside his body, the Yang energy focuses entirely on fixing his internal system. The serum repairs his broken pathways and forces his blocked chakra valves to open naturally. For the first time in his life, Lee can project chakra outward. Because the serum spent energy healing him, he only gets a moderate boost to his chakra reserves compared to the others. However, he can now successfully learn techniques that require external projection, including the Tempest Kick.
The group would spend the remaining two years training and improving, Kakashi creating more serums for the other senseis (including Shizune), Tsuande, Mei, and some spare ones for whoever wants to take them, the vials safely stored in his base.
- Chapter End -
There was no way to make this chapter anything more than a description of some of the events in-between the years, but here it is; the start of Shippuden is in the next chapter.
The serum would have affected all the jonin sensei in normal, but useful ways, like Tenten and Sakura, but Tsunade and Mei would have something more; you'll see next chapter when I show you the changes as I did with the other, but next chapter will be a proper chapter.
They may seem op, but I assure you that they're not all suddenly village-ending threats or anything that ridiculous… well, some of them are, but they were already before the serum.