Kaidou's rain is a signal, a command he sends to the Eight-Headed Dragon. It's not merely a mount; in Kaidou's eyes, it is a special "companion" capable of fighting alongside him.
In terms of his own strength, the Eight-Headed Dragon cannot assist him in direct combat; it's mainly for transportation, clearing out soldiers, and controlling the weather.
Depending on the power of a Pokemon, the rain cloud created by Rain Dance varies in scope. The Eight-Headed Dragon charges into the distant clouds to create a larger rain cloud in a short time, and it can infuse the power of thunder into it, transforming it into a thunderstorm cloud.
This is not ordinary natural lightning but artificial lightning induced by Pokemon power. Kaidou also possesses some Pokemon powers within him; skills like Dragon Dance and Protect are triggered by that power.
This special power emerged after slight bodily changes when learning skills in the space created by Arceus. With this power, Kaidou can manipulate the thunder in the cloud for specific effects.
The Eight-Headed Dragon doesn't know what Kaidou intends to do; it merely follows his previous instructions to release some skills. The rest are Kaidou's calculations in his mind.
Tenma Daijizaitenjin was initially Charlotte Linlin's skill, allowing her to control the thundercloud, Zeus, to indiscriminately bombard the surroundings with lightning.
The lightning released even has consciousness, changing direction to track evading targets.
The speed of lightning is inherently fast, which is almost unavoidable, a terrifying AoE.
As the older sister on the ship back then, Charlotte Linlin greatly influenced Kaidou. Devil Fruits, the techniques of the Giant Race, all came from her, and Kaidou learned a lot from her, intending to replicate some of Charlotte Linlin's moves now.
In his Dragon Form, he can also use lightning, but not as extensively as Zeus. Now, with the help of the Eight-Headed Dragon, he can fight alongside his battle pet like Charlotte Linlin.
Or rather, the idea of fighting together with the Eight-Headed Dragon took inspiration from Charlotte Linlin, whose Homies created from her soul were a significant force.
"Evaluate this move! Navy Hero!"
Grasping Hassaikai with both hands, Kaidou swung down with force. It seemed like he was pulling down the sky, forming a terrifying curtain of lightning, countless bolts converging together, descending with a mighty force.
"Damn..."
The rain pounded on Garp's body, his clothes soaked by the heavy rain. The rising storm cloud had already blocked out the sun, but the G-1 Branch remained as bright as day, the glow of lightning becoming a new sun.
Garp was not unfamiliar with Tenma Daijizaitenjin. At that time, Kaidou had not yet grown, and Charlotte Linlin was still a core member of the Rocks Pirates. The lightning she unleashed was always a major problem on the battlefield.
Though Zeus was a Homie she created, its true form was a cloud. Under Charlotte Linlin's command, it could freely traverse the battlefield for devastating pinpoint explosions.
The Tenma Daijizaitenjin Kaidou now wielded surpassed the one that Charlotte Linlin used in his memory.
Moreover, Kaidou differed from Charlotte Linlin; he didn't just unleash an attack. As the lightning descended, Kaidou had already reached Garp, bathed in the lightning glow, like donning armor of lightning.
"Descent of Three Worlds·Hiku Naraku, Thunderous Fury!"
The sky filled with thunder transformed into frenzied silver serpents, compressed together under the guidance of Kaidou's weapon.
Garp's movements remained unchanged, but his clothes instantly burst apart. Though aged, every muscle was well-defined, now turned pitch-black under the baptism of Haki.
No matter what means the enemy employed, his fighting style didn't change: if one punch wasn't enough, then two. As long as his fists were strong enough, he would always break through the enemy's defenses.
As fist and club collided, the power of lightning and Haki exploded. The compressed thunder shattered completely, and after the roar, the battlefield seemed to enter a new silence.
...
Inside the G-1 Branch, a Navy soldier crouched in a corner, covering his ears. The sturdy wall was enough to withstand cannon bombardment, yet failed to provide him any sense of safety.
For a long time, he couldn't discern what was happening outside until a colleague beside him patted his shoulder. He couldn't hear a sound, only see the constant movement of his colleague's mouth.
"Talk! I can't hear you!"
But he still heard nothing. Under his companion's guidance, he realized his hands were stained with blood, the source being his ears.
Such situations were not isolated; even distant from the battlefield, many Navy soldiers' hearing and sight were impaired from the previous clash.
Both Kaidou and Whitebeard didn't wish to ignite a war in their territories because they knew the aftermath's consequences.
Once outside calmed, a few soldiers continued observing the situation; the G-1 Branch's sturdy walls had collapsed, and even a chunk of the island's land inexplicably vanished.
At this moment, a deep pit surrounded Kaidou and Garp, with bricks occasionally falling in, and those outside couldn't hear the impact sounds from the pit's bottom.
"It truly is formidable Haki, taking all the attacks head-on."
Kaidou's attack was not solely aimed at Garp; the overflowing lightning was sufficient to impact nearby Navy, but Garp forcefully suppressed Kaidou's lightning before it exploded, with his body and the ground underneath bearing the strike.
This attack was more about range; its single attack power wasn't that strong, yet Garp forcefully took the full-powered strike, protecting most of the Navy soldiers.
"You lunatic, that lightning affects you too, doesn't it?"
Such an attack couldn't make Garp lose his combat ability. He even noticed that Kaidou hadn't avoided the lightning's effect either, a testament to its considerable side effects.
"Wughahaha, it's just a minor irritation that'll pass soon enough."
"If a guy like you escapes, the sea might become even more chaotic..."
Garp's body rapidly recovered under Life Return, metabolizing quickly to rid the lightning's influence. Looking at the damaged branch and land around them, Garp resolved to prevent Kaidou's departure.
"This is a Navy Branch, not a place you can come and go as you please! Bone Fist·Stars!"