The sea swallowed him whole.
His limbs went completely numb—the classic curse every Devil Fruit user had to face.
Eating a Devil Fruit granted a special ability that split into three types: Logia, Zoan, and Paramecia.
The fruit Cain ate was not one of Caesar's cheap copies. It was a flawed version of the Azure Dragon Fruit, made by the genius scientist Dr. Vegapunk.
It was a failure sure, but it was much better than Caesar's work.
The only difference was the color it gave the user.
Even as a copy, it beat most fruits. The real Azure Dragon Fruit belonged to Kaido, one of the Four Emperors.
The man was known as the strongest creature on land, sea, and air.
That alone proved the fruit's massive potential.
By rights, Cain's fruit should be called the Fish-Fish Fruit, Mythical Zoan Model: Pink Dragon.
It gave him the power of a dragon and since it was called Fish-Fish Fruit, he should be able breathe underwater.
But the sea still hated Devil Fruits.
Underwater, he lost all his strength and just kept sinking.
As Cain watched the bright surface of the water drift further away, his mind went back to the day he met Luffy—the day Luffy's dad, Dragon, handed him to Garp.
....
Cain was a reincarnator from another world.
At first, his mind was cloudy.
His body was just a baby's, making it hard for him to form real thoughts.
When he finally opened his eyes, he was drifting on the open ocean inside a wooden tub.
Abandoned at birth, he had no clue who his parents were.
That tub was the only reason he did not drown.
By sheer luck, Dragon spotted him while dropping off Luffy, picked him up and handed both of them to Garp.
"This is Luffy, and this is Cain. From today on, these two are brothers."
Garp stood with his hands on his hips.
He looked down at the two babies and poked them.
Then, he got serious. "You two better grow up fast and become strong Marines."
'Old man, why are you making speeches to babies? Can Luffy even understand you? Also, stop poking me!'
Cain wanted to yell but could not talk yet. He felt a tug at his foot and looked over.
Luffy was happily chewing on his toes with a giant grin.
....
'To think I remember something from that far back... That idiot could even laugh while eating a foot...'
The sea currents messed up Cain's hair.
His senses actually felt sharper down here.
'Is this the Fish-Fish Fruit doing its thing?' he wondered.
'Come to think of it, Luffy will be setting sail soon... And Ace... I really can't afford to fall behind.'
A spark lit up in Cain's eyes!
Up on the surface, Garp keep yelling his ass off.
"Cain! You okay?! Grandpa's coming to save you!"
Boom—Crash!
The water exploded and Cain burst into the air, gasping for breath as he kicked off the sky using the Moonwalk technique.
The sea weakens all Devil Fruit users.
But for Cain, weakness was a daily routine. Surviving Garp's insane training meant going through a worse hell than even Luffy did.
After taking that kind of abuse, feeling a little weak in the water was nothing.
(Luffy could carry boulders while wearing Seastone cuffs, so this was hardly a shock.)
Thanks to the Azure Dragon Fruit, his underwater breathing and years of brutal workouts, using Moonwalk to escape sinking was easy.
(Complete BS imo.)
Still, Cain hit the dirt and glared at his grandfather. "Old man, are you trying to kill me?"
"Gahahaha! You got out fine, didn't you? i was going to jump in anyway. And watch your mouth, brat! Who are you calling 'old man'?! Say 'Grandpa'!"
Thwack!
Garp brought his Fist of Love down on Cain's head.
"Huh?" Garp stared at his knuckles. "That didn't feel right. Since when is your head so hard?"
Cain smirked.
Even without transforming, his skin was now as tough as Kaido's dragon scales.
"Sorry for making you worry, Grandpa." Cain dusted himself off and got serious. "I didn't ask you to bring the team here just to catch Caesar. I wanted this fruit too. It isn't one of Caesar's experiments. Vegapunk made it."
"Huh!? I knew it! No wonder you used my name to snoop through Vegapunk's files and bother Kizaru." Garp nodded, a massive grin spreading across his face. "So, you gained a pretty terrifying power?"
"Yep. One you know very well. I want to test it out. How about a spar, Grandpa? It might get messy. Did you finish loading up the prisoners?"
"it all handled." Garp turned and waved at Bogard on the warship. "You guys set sail! Don't wait up!"
Once the ship was out of sight, Garp turned back.
He dug his pinky finger deep into his nose and raised an eyebrow. "Alright, Its just us now. What's this about mystery power?"
"Watch closely."
Cain's aura flared.
His eyes went sharp and feral. His skin took on a pink tint as his face stretched out. Fangs grew in, and a sharp horn pierced through his hair.
Garp stopped picking his nose. "Th-This is!?"
Cain shot up.
Flame clouds materialized around his feet. He kicked off the ground, his body expanding and covering in thick pink scales.
A massive tail whipped behind him as he grabbed the clouds, floating into the sky.
In seconds, he was a colossal dragon circling the island!
Garp threw his head back and laughed.
"You brat! That's is Kaido's power!"
He was thrilled his grandson had gotten such an insane power—and even happier the Marines had it instead of some pirate!
"Not just that, Grandpa. Watch this."
Hovering as a giant dragon, Cain looked down at Garp as a massive, heavy wave of pressure built up in the air around him.
"Oh ho! So you really have that too huh?! Perfect! Let's have a loving training session with your grandpa!"
"Mhm."
Cain closed his eyes and nodded his massive head.
With this kind of power, he was ready to clash with a top-tier monster like his grandfather!
"Bring it."
Cain snapped his eyes open, ready to unleash his haki.
But Garp's fist—coated in pitch-black Armament Haki—was already an inch from his snout!
"Wait—"
Boom!
The massive dragon head snapped back and slammed into the dirt.
The giant body crashed down right after it.
The whole island shook, kicking up a massive cloud of dust as the ground cracked wide open.
'Are you kidding me?!'
'Who goes straight for the face right out of the gate?! Grandpa... That is not how these fights are supposed to work!'
'When I unleash my Conqueror's Haki, you are supposed to clash it with yours! That is the unwritten rule!'
'Then I use my Devil Fruit, we trade a few hits, and even if I lose, I switch to my hybrid form so I at least get a decent defeat scene!'
'You don't just sucker-punch me in the snout before I even finish my pose!'