The desert sun baked the air until it shimmered. Kakuzu's sutures writhed like venomous snakes in the heat haze, his gaze fixed intently on the man standing dozens of paces away.
Setsuna stood quietly, without any extraneous movement, his breathing so light it seemed to merge with the wind and sand.
"Since you destroyed one of my hearts, I'll take yours to replace it," Kakuzu's eyes were cold. The Fire Release mask and Water Release mask lit up simultaneously, "Fire Release: Intelligent Hard Work! Water Release: Water Formation Wall!"
A sea of high-temperature flames and a high-pressure water cannon collided mid-air, instantly generating a steam explosion covering a hundred meters.
Through the steel-melting cloud vapor, Kakuzu saw Setsuna's figure piercing straight through, his body enveloped in a crimson halo from the violently evaporating moisture.
"Lightning Release: False Darkness!" The Lightning Release mask bulged from Kakuzu's back, countless lightning spears intertwining into a net.
Setsuna abruptly changed direction, the shockwaves from his kicks against the air tearing a gap in the lightning net.
He spun mid-air, his left leg descending like a battle-axe. The Earth Release: Earth Flow Wall Kakuzu hastily erected was split in half by the kick, the residual force carving a kilometer-long trench in the desert.
Earth Grudge Fear's tendrils seized the chance to entangle Setsuna's ankle. A ruthless glint flashed in Kakuzu's single eye. "Combination Ninjutsu: Divine Punishment Flame!"
Instantly, the sky was torn asunder. Countless lightning spears fell from above, each bolt exploding into a blazing white fireball upon impact.
The desert melted into glass-like pits under the extreme heat. Waves of fire swept across hundreds of meters, setting even the air ablaze.
The Genin panicked and fled for their lives, avoiding the aftermath of the battle. Only after escaping several hundred meters away did they have the presence of mind to watch the fight.
"So powerful! Is this Setsuna-sama's true strength?" An Iwagakure's Genin stared dumbfounded. If he had previously given up on certain unrealistic ideas only because of Setsuna's powerful summon, now he was astounded by Setsuna's own power.
"So strong!" Natsuhi was shaken. Not just Setsuna, but that assassin was terrifyingly strong as well.
'Large-scale Ninjutsu came effortlessly to him, even combined freely. Compared to him, the Jonin of Hoshigakure seemed as weak as Genin.'
Setsuna's figure moved through the thunder and fire. His speed surpassed visual capture. With each step, the sand beneath his feet exploded into huge depressions.
The moment the lightning struck, his fist was already hammering towards Kakuzu's face.
Kakuzu's pupils contracted sharply. Earth Release: Earth Spear was instantly activated, while the Water Release mask lit up. "Water Release: Water Formation Wall!"
A high-pressure water wall erupted from the ground, but Setsuna's fist didn't hesitate in the slightest, piercing straight through the water curtain and smashing heavily into Kakuzu's chest.
The Earth Spear was as brittle as clay under the fist. Kakuzu's body flew backward like a cannonball.
"What a monster. While he doesn't have the despair-inducing power of the First Hokage's Wood Release, this level of monstrous strength might even surpass the First Hokage," Kakuzu coughed up black blood while frantically repairing his damaged body with Earth Grudge Fear's tendrils.
"From what you're saying, it seems I'm considerably weaker than the First Hokage?" Setsuna asked.
"Haha, humans cannot imagine power they haven't witnessed. You are indeed strong, but you are still far from Senju Hashirama," Kakuzu promptly transformed into a 'Hashirama fanboy'.
Setsuna didn't doubt this. He could be considered overwhelmingly powerful within the Kage-level, but Hashirama had long surpassed that level.
At the very least, without going all out, he had no confidence at all in suppressing the Nine-Tails, whereas Hashirama suppressed the Nine-Tails as easily as playing.
"Even so, it still makes me a bit unhappy," Setsuna flexed his fists.
Watching Setsuna walk towards him, his speed increasing with each step, Kakuzu slammed his hands on the ground. "Earth Release: Earth Dome Wall!"
The entire desert began to tremble. The ground swelled into a rocky mountain a hundred meters high. Countless sharp stone pillars stabbed out from underground like the fangs of a giant beast.
Setsuna's figure weaved between the stone pillars, each dodge accompanied by the sound of exploding air.
Kakuzu didn't dare pause for a moment. Lightning Release and Water Release activated simultaneously. "Lightning-Water Combination: Torrential Lightning Prison!"
High-pressure water pillars erupted from underground, each stream entwined with high-voltage lightning, forming a deathly lightning web covering the battlefield.
"To use Water Release of this scale in a desert... truly impressive," Setsuna praised sincerely. Kakuzu wasn't particularly outstanding in the future Akatsuki, but his foundations were undoubtedly terrifyingly solid.
"But, it's useless." Setsuna's body spun, a nimble and agile divine dragon soaring into the sky. "Konoha Shinryu!"
This time, he didn't stay outside the 'dragon' but hid within the dragon's eye, steering the fierce wind to charge towards the deathly lightning web.
Swept up by the gale, the thunderstorm and water pillars also merged into the divine dragon, transforming into a thunderous waterspout connecting the sky and land.
Sand scorpions and giant ants hiding underground were swept into the sky, vanishing under the thunderous blows without even a chance to scream.
Witnessing this terrifying scene, the examinees were struck speechless with horror, only able to flee for their lives once more, not daring to stop for a moment.
"Don't think I'm afraid of you!" Kakuzu's sutures writhed madly. Two hearts and his main heart pumped Chakra simultaneously, "Fire-Earth Combination: Lava Hell!"
The ground instantly melted. Scorching magma gushed from the fissures. Waves of fire mixed with rock, forming a destructive lava domain.
Kakuzu stood at the center of the lava, the Water Release mask glowing, forming a high-pressure water membrane around him to resist the high temperature.
The thunderous dragon crashed down, violently colliding with the lava domain Kakuzu had created.
Boom!
It was as if a meteor had struck. The terrifying shockwave blasted away the sand and stones within a kilometer radius, like a sandstorm falling from the sky.
Amidst the sky-blotting sandstorm, a figure was sent flying violently.
This figure was naturally Kakuzu. His vision swam, as if returning to the moment he assassinated the First Hokage. "Is this my end?"
"No... I still want to live..." A yearning for life surged in Kakuzu's eyes.
However, Setsuna's figure closed in like a persistent shadow, his right fist aimed straight for Kakuzu's heart.
The protective membrane from Kakuzu's Water Release shattered like glass under the fist. The Fire Release and Lightning Release masks lit up simultaneously, attempting a final counterattack… but it was too late.
"It's over." Setsuna's fist pierced through Kakuzu's chest. The three hearts shattered simultaneously under the impact.
The Earth Grudge Fear's tendrils fell limply. The dying Rogue Ninja uttered his final words: "Your head... could be sold for a lot of money..."
Before his voice faded, the final sutures turned to dust in the fist wind.
The desert returned to silence, only the sizzling sound of cooling lava echoing.
"Still thinking about money until the very end. I suppose that fits his character," Setsuna shook his head, somewhat curious.
'Asuma in the future had a bounty of 35 million ryo. I wonder how much my head is worth at the underground exchange.'
---
Author's Note: Regarding Setsuna's combat power, my main concern is that people might say I've written the protagonist too weak, questioning how he could possibly be inferior to Senju Hashirama. So let me explain my understanding here. In most cases, Ki and physical strength are proportional, but there are a few exceptions. For example, Master Roshi's physical strength declined due to old age, but his Ki kept growing over 300+ years of training, allowing him to destroy the Moon at full power. Then there's Piccolo, whose body was restored to youth, but his Ki had stagnated due to 300+ years of sealing, so his full power only allowed him to destroy a town. Without this understanding, it's hard to explain why Piccolo, who was stronger than Master Roshi, only managed to destroy a town even when sweating.
(Piccolo also has a Moon-destroying feat, but that was the second-generation Piccolo, and during the period when he was training Gohan after fighting Raditz, his power level was probably close to 1000.)
As for why Master Roshi was afraid of Piccolo, I think there are two possible explanations. First, Master Roshi's Kamehameha, while large in quantity and range, lacked sufficient quality to kill Piccolo. Second, Piccolo could dodge it. And Piccolo's body was far stronger than Master Roshi's, allowing him to kill Master Roshi after he used the Kamehameha. Of course, one could also argue that Dragon Ball was a comedy manga in its early stages, so we shouldn't overanalyze the power levels.
If we must obsess over the Moon-level power, we can compare it like this: Otsutsuki Toneri cut the Moon in half, then lost to Naruto. At that time, Naruto no longer had the Six Paths Senjutsu given by Hagoromo, and he defeated Toneri using his own power and the Nine-Tails'. This version of him isn't necessarily much stronger than Hashirama, so it shouldn't be too problematic to say Hashirama possessed near-Moon-busting power.
In summary, the setting here is that Setsuna is in the top tier below the Super Kage-level. In some aspects, he can already be considered Super Kage, but overall, he is still inferior to Hashirama.