Aburame Tetsumaru had chosen this remote, desolate island as his testing ground for two reasons: its isolation and the fact that it was an active volcano.
By "planting a mushroom" here, he hoped to remain undetected. Even if someone noticed the commotion, the volcanic eruption would serve as perfect cover.
However, he hadn't anticipated the massive chakra fluctuations the "mushroom" would produce. Now that the volcano had been fully awakened, even its natural fury wasn't enough to mask the activity. After all, a typical volcanic eruption doesn't radiate the signature of high-density chakra.
He had to retreat immediately to avoid being cornered.
Tetsumaru wasn't worried about the Hidden Mist Village fifteen hundred kilometers away, the Hidden Sand two thousand kilometers out, or even the frantic Konoha. His concern was directed upward: the Otsutsuki clan on the Moon, who possessed the Giant Tenseigan and took the surveillance of the Shinobi World as their self-appointed duty.
He hadn't been worried about launching rockets or satellites. The chakra signatures of the Rocket Bugs, Satellite Bugs, and even the Overlord Bugs were negligible—hardly enough to catch the attention of those on the Moon.
As for their size, it was a non-issue. Compared to the Shinobi World, which spanned nearly ten thousand kilometers in diameter, even the largest Overlord Bug was a mere three hundred meters across—less than one-hundred-thousandth of the world's scale. The Satellite Bug, with its twenty-meter wingspan, was even smaller.
If one were to imagine the world as a one-meter globe, the Satellite Bug would be a speck of dust clinging to its surface, barely 0.005 millimeters in diameter. It was invisible.
But a massive chakra fluctuation was a different story. As one of the pinnacle achievements of the chakra system, the Giant Tenseigan couldn't possibly be insensitive to such energy. This "mushroom" had produced a spike exceeding that of a Four-Tails Jinchuriki; to the Tenseigan, it likely looked like a blinding flare in the dark.
Then again, perhaps it wouldn't matter. The chakra released during the legendary battles between Hashirama Senju and Madara Uchiha was undoubtedly far more violent, yet the Otsutsuki hadn't descended to intervene then.
Perhaps they had watched, but after careful consideration, they realized that going down to face those two monsters would be a death sentence. So, they simply lay down and pretended not to see.
Regardless, if there was a possibility of trouble, it was best to leave early. Tetsumaru left behind a multitude of insects to act as sentries, curious to see if any "demons or gods" would actually be lured in.
If they were, he'd have to find a way to deal with them. He still had plenty more mushrooms to plant.
First, he needed data for formal deployment, though that wouldn't require many tests. He needed one air-dropped live test using an Overlord and likely three more to test the integration of the Rocket Bug as a long-range strike weapon.
Only through live usage could he determine the time required from preparation to deployment, and from arrival to detonation. These metrics were essential for deciding when and where to "plant a mushroom" on a battlefield.
Next came the data for upgrading the payload, and that would require many mushrooms.
A "Tier 2 mushroom" (a fusion bomb) required a temperature of one hundred million degrees to ignite, necessitating the smallest possible fission bomb as a trigger. To hasten the initial tests, Tetsumaru had used a Sealing Scroll to bypass the "implosion threshold."
However, the path toward miniaturization couldn't ignore this technology. Implosion-type designs used conventional explosives to compress the uranium fuel, artificially increasing its density. Combined with a neutron reflector, this could drop the critical mass required for detonation down to six or seven kilograms.
With that as a base, and adding various specialized components, one could create a "mushroom" weighing less than twelve kilograms.
Once the implosion method yielded the smallest fission trigger, he'd need accurate data on shockwaves and thermal radiation within 0.2 seconds of detonation. Only then could the fission bomb serve as a reliable trigger for a fusion device.
After enough fusion tests to gather data on ignition, he could complete the upgrade to Tier 3.
Tier 3 mushrooms were the specialized variants: Neutron bombs, EMP (Electromagnetic Pulse) bombs, shockwave-enhanced bombs, plasma weaponry, and laser-based nuclear-pumped weapons.
In Tetsumaru's view, Tier 1 and Tier 2 mushrooms were too powerful; they were deterrents, "trump cards" to keep his backbone straight. They were difficult to use in actual combat due to too many constraints. Only the Tier 3 variants, with their controlled effects, were true practical weapons—things that could eventually be integrated into his Bio-Armor and insect swarms.
With so many experimental requirements, a suitable testing ground was precious. He wouldn't give it up easily.
Ten days later, the second mushroom was prepared.
The insects left at the site had detected nothing. A small portion had died from radiation, but the majority were thriving—more energetic than before.
Since no one had noticed, the plan continued.
This time, Tetsumaru opted for an underground tunnel detonation. The surface-level commotion would be smaller, and more importantly, it was easier to capture detonation data.
The Mining Zerg spent fifteen days excavating the cave. Beyond the main tunnel, the Mole Crickets dug over four hundred palm-thick pipes in a radial pattern centered on the detonation point.
When the mushroom exploded, the shockwaves, light, heat, and electromagnetic radiation would travel down these pipes without interference, allowing him to collect "clean" data.
Upon arrival, Tetsumaru entered the tunnel from underwater. He installed sensors in every pipe to record the aftermath.
This time, he specifically added chakra monitoring equipment. He even planned to approach the site himself, using his Insight ability to directly experience the chakra tide of a nuclear explosion.
Donning heavy lead armor and sealing the massive blast doors, Tetsumaru commanded the Mushroom Bug to walk to the center. Then, it detonated.
Tetsumaru closed his eyes, pushing his Insight to its limit. He observed the grand chakra circulation within his own body while indirectly sensing every change at the epicenter.
First came the thermal radiation, then the plasma ball appeared... Wait?
When the plasma ball expanded to about three meters, it experienced a momentary internal collapse—an infinitesimal blip in time—before expanding again.
In that single instant, an unmeasurable amount of chakra manifested. The volume was so vast and immense that it created a powerful chakra shockwave. This wave merged with the thermal blast and the hurricane-force winds of the plasma expansion, nearly doubling the destructive power of the mushroom.
Fascinating. Chakra can be produced without the union of spirit and physical energy.
No, I shouldn't be so hasty. Perhaps it isn't "produced," but "extracted" from somewhere? Or perhaps it's a byproduct of the fission reaction itself?
This is truly interesting.
The subsequent changes were standard. Beyond correcting some errors in his previous data, there were no further surprises. The experiment was a complete success.
The next test would be an air-drop by an Overlord Bug. As for the second underground test, it would have to wait. It wasn't that he couldn't build another mushroom, but the blast had vaporized over four hundred sets of expensive testing instruments. His stock was depleted, and he couldn't simply buy more off the shelf.
The market for high-precision testing equipment in the Shinobi World was tiny; production and sales were both stagnant. He had burned through four hundred sets in a single day—more than the entire world produced in a month. Manufacturers couldn't ramp up production overnight, so Tetsumaru could only place an order and wait.
With the experiment over, Tetsumaru prepared to head to the surface to survey the site before returning to Broodmother Island.
As he walked up the tunnel, he habitually activated his Secret Technique: Domain Field Barrier. Suddenly, his insects spotted a figure.
A man was floating in the sky.
Tetsumaru's blood ran cold. Without a moment's hesitation, he turned back toward the underwater exit.
Flight was an exceptionally rare ability in the Shinobi World. Ninja who used gliders or specialized tools were one thing, but those who could fly using pure jutsu were never weak.
The figure he just saw had no wings, no floating rocks beneath his feet, and no clay birds. He was hovering in the air through sheer will.
Is it the Earth Style: Super Light-Weight Rock Technique?
Doesn't look like it. The man has a normal build, not a short one, and he's not wearing a Hidden Rock headband.
Tetsumaru retreated deep into the sea, stopping only when he was two kilometers away from the test site. At this safe distance, he began to activate the ninja insects he had hidden in the area.
Linking his Domain Field to the scouting Dragonflies, Tetsumaru finally got a clear look at the intruder.
Immediately, his mind filled with questions: Who is this?
The man was quite tall with a strange hairstyle—shaved on the sides, but with long hair on top tied into a ponytail draped down his back. Beneath his left eye was a black tattoo of the Roman numeral IV, and on his chin was a black diamond mark. He wore a white robe with a red neck guard, wrist guards, and earrings.
Despite such striking features, Tetsumaru couldn't find a single person in his memory who matched the description.
The man circled the test site in the air before landing to inspect the ground. He peered into the crater of the still-erupting volcano and used jutsu to drill several holes into the ground where the explosion had occurred.
After a long while of poking around, he found nothing of value except for a few pieces of vitrified rock.
Finally, the man tossed a piece of glassified stone in his hand and muttered to himself, "So, it was chakra released from the earth's core fire. A rare instance of chakra that doesn't belong to Kaguya... pity the quantity is too small."
"Hmph. Even if there were more, I can't absorb and use it right now. Meaningless."
With that, he tossed the stones aside and flew away.
He's finally gone. I have no idea who that was. The waters of the Shinobi World are far deeper than I thought; there are powerhouses existing completely outside the original plot. I thought Kaguya Otsutsuki's appearance had already drained the pond and forced all the big fish out.
Wait... Tetsumaru froze. A powerhouse that Kaguya's resurrection didn't force out? The villains from the Boruto sequel matched that description.
Though he hadn't watched the sequel—which was often mocked as "unburnable garbage"—Tetsumaru had picked up fragments of lore through short videos and fanfiction. He knew about the hidden or newly arrived "alien Otsutsuki."
That was a living alien. An incredibly precious research specimen.
He couldn't handle it yet. But in the future, when he was strong enough and his control over the world was absolute, he would hunt him down, drag him into the lab, and study him thoroughly.
Tetsumaru smirked. "I've memorized your face. I won't keep you waiting long."
"Strange. An actual Otsutsuki was lured in, but where are the Moon Otsutsuki?" Tetsumaru looked toward the sky. The moon wasn't visible in the bright daylight, but he knew exactly where it was. "When will they show up?"
Having encountered an unexpected prowler, Tetsumaru's cautious nature (his "cowardice") was triggered. He decided to pause the practical field tests and focus on underground detonations to avoid being caught red-handed.
Two months later.
Tetsumaru cautiously completed his final mushroom test of the year. The Moon Otsutsuki had still not appeared.
After the experiment, for safety's sake, Tetsumaru left the site via the seabed, swimming for a full fifteen kilometers before surfacing. The process was a massive waste of time.
But after two months of being "cautious," it seemed he had done it for nothing. Tetsumaru finally grew irritated.
Otsutsuki, are you coming or not? Give me a straight answer! Being left hanging like this is driving me crazy.
He stood on the ocean surface, glaring at the full moon in the sky, and spat out a curse: "You damn Otsutsuki... just wait. Once I reach the moon, I'm coming for compensation. If you don't pay up, I'll scatter your ashes personally!"
The Otsutsuki: ...We were just minding our own business, what did we do to you?
Tetsumaru had misjudged them. At this moment, the Otsutsuki clan on the Moon was on the brink of civil war. The tension between the Main House and the Branch House had reached a breaking point.
Both sides were armed and ready, terrified that the other would strike first. They had no time to worry about the Shinobi World below.
In a forbidden area of the Branch House, six middle-aged white-eyed ninja were discussing their battle plan.
"First, we assassinate Chigetsu. That will force the Main House to frantically mobilize their forces. Then, we strike the Main House compound with half our strength, locking them in a stalemate."
"The decisive move will be led by me personally. I will take our most elite warriors to storm the Holy Land. We must control the Giant Tenseigan at all costs. Then, we use the Tenseigan to wipe out the Main House."
"Is it that simple?"
"It has to be. Any more complexity and the Main House will take advantage of our scattered strength to defeat us one by one."
The group fell silent for a moment, then nodded.
The Main House was the Main House because they were powerful. Although their numbers were small, their advantage over the Branch House was still overwhelming.
"And after we win? What about the survivors of the Main House?"
"Kill them all."
"All of them? Even the children..."
The leader of the Branch House snapped. "Even the smallest member of the Main House is still the Main House. If they grow up, they will be a massive problem. None can be left alive."
"But they are the descendants of our Ancestor. This is going too far."
The leader's eyes narrowed. "Fine," he said, voice dripping with fake piety. "Then we will sacrifice them all to the Tenseigan. Let them become one with the Ancestor."
Hearing the prospect of "merging with the Ancestor," everyone nodded. That was the highest honor. If they framed it that way, they didn't have to feel guilty about the slaughter.