There were reasons he'd used his power on Uta without telling anyone…
First, Luffy needed to understand his own limits. Experiments on inanimate objects could be done in secret, but testing effects on living beings—especially humans—was difficult to conceal.
Initially, he'd considered using villagers as test subjects. But any alterations to Uta, an outsider, would go unnoticed by the locals. Moreover, Shanks and his crew avoided involving unrelated people unnecessarily, maintaining minimal contact to prevent drawing hostile attention.
However, Uta—despite calling herself the Red Hair Pirates' musician—was often told by Benn Beckman that she wouldn't grow properly within the ship's cramped community, so she frequently interacted with the villagers.
Thus, she was an eternal outsider to the villagers, and someone the Red Hair Pirates didn't constantly supervise, an ideal test subject.
Second, he wanted to uncover Uta's true nature.
At first, he suspected she might be another world-hopper like himself. But no matter how many times he applied the Tag-Tag Fruit's power to interrogate her or read the information embedded in her tags, he found nothing suggesting reincarnation or outside knowledge.
His conclusion: Uta was either a character he didn't recognize or a native of this world whose existence stemmed from his own arrival. Either way, she posed no threat—but having used his power on her, he couldn't simply discard her. So he continued his experiments on her body.
"L-Luffy..."
"What?"
"I-I can't... anymore... please... "
Her face utterly debauched, she pleaded. Watching her right hand mechanically working between her thighs, tears in her eyes, Luffy smirked. "Can't be helped," he said, tugging the leash toward home.
"Luffy! Luffy!! Luffy's cock... "
Once inside, she pushed him down at the entrance, fumbling with his pants. Before his erect member, Uta licked her lips hungrily. Her pupils had fully morphed into heart shapes; she was completely in heat.
"Uta. Stay."
"Ghh——!!!"
Her body jerked violently at his command, then she climbed off him and sat seiza, waiting. The picture of a dog holding a position for a treat.
Unaware of herself, her mouth hung slack, tongue darting out as she imagined what was to come. Panting despite not having run, her warm breath humidified the air.
"Good girl."
He shed his clothes and presented his cock again. Uta's face twisted with barely restrained desire; she leaned forward from her kneeling position, crawling on all fours toward him.
"Go ahead."
"…"
Permission granted, she took his dick to the throat in one motion, beginning to slurp noisily.
"Mmph... chup... haah, delicious... Luffy's... cock..."
She savored him like a popsicle, coating him meticulously with saliva. But she hadn't forgotten her training, occasionally she'd pull back to lick the frenulum, the glans, the balls.
Within seconds, his cock was slick with her spit, too large for her small hands to encompass.
"Uta. Stop."
"Slurp... buh... Yes!!"
She obediently released him. Usually, after preparation, he'd fuck her holes.
Sometimes anal, sometimes vaginal, sometimes her throat— cumming even on her nostrils on occasion.
"Today, I'll come wherever you want."
"Really?!"
"Yeah. You're leaving for Elegia tomorrow, right? This is a special treat."
The Red Hair Pirates occasionally departed on expeditions from Foosha Village—supply runs, clashes with rival crews, and various reasons. Dangerous ones left Uta behind, but the next destination was a so-called music kingdom.
Uta, who loved singing, would be allowed to accompany them; even pirates were welcomed there under conditions of no looting.
"So? Where do you want it?"
"Um, umm!"
She pondered like a child at an ice cream stand, but her expression was entirely inappropriate for a girl her age.
"Then... my pussy? Is that okay?"
"Huh, unusual. You always said you wanted the front to be last."
Despite his training, Uta had preferences. She liked saving the best for last—the vaginal canal, where she felt sex most intensely, was her usual finale.
"Hehe... sometimes, you know..."
Her bashful tone meant she was hiding something. He could easily check with her body tags or manipulate her perception tags to find out. But there was no need.
"Fine." He pushed her down.
"Eep... hehe... hey, Luffy. Hurry."
Despite being about to be fucked, Uta spread her legs lewdly, using her fingers to part her slit. Her pussy, which had accommodated his cock countless times, was already loose enough to accept him immediately.
"Hold on. Let's try something different today."
From among his collection of tags, he selected certain information and applied it to himself.
"Alright. Here I go."
"Uh-huh!! Come on."
Luffy lowered his hips and pushed his cock in—a slick sensation greeted him. Under normal circumstances, Uta's underdeveloped body would have screamed in pain, tearing from the center outward. But he'd swapped her pain perception with pleasure using his ability.
"Hngh!? Ugh...!"
Her voice sounded strained, but her expression was blissful; anyone could see she was biting back not pain but ecstasy.
"Ah, it's inside!! Luffy's cock inside me."
Each thrust made her moan, clearly enjoying herself. He knew all her weak points; striking them made her cry out even higher.
"Hih, ah… Twitching, it's twitching!!"
"Yeah, I'm coming…"
They'd coupled so many times counting was pointless. Uta's body remembered his timing, his tells. Before he said anything, her cervix descended, enveloping his glans as if to catch every drop.
"Higii!! Coming! It's coming! My pussy wants Luffy's cock so bad!!"
"Here it comes."
"Nyaaahhh!!!"
Her climax coincided with his release. The force arched her back like a shrimp. Normally, ten-plus seconds of ejaculation would end one round, Uta drowning in pleasure.
"Wha...!??"
But the ejaculation didn't stop. Her lower belly gradually swelled. Her uterus, already flooded with semen, threatened to overflow, pushing against his shaft.
"It won't... won't come out!!?"
His cock was snugly lodged in her pussy, no gap for leakage. Still, more semen poured in, expanding her uterus from within. The pressure became intense pain—which swapped into pleasure—stimulating her brain.
"Hah Hah Haah I'm gonna die, my pussy's gonna break!!!"
Not just sensation—her physically distended uterus began crushing her internal organs. Literally fatal pleasure consumed her, and Luffy felt a twinge of regret.
"Guess this body can't handle a dog's ejaculation after all."
The tag he'd applied to himself: Canine Ejaculation, taken from a stray dog in Foosha Village. Dogs, when cumming, swell a bulb at the base of their penis, locking them inside the female. That was why he couldn't pull out, why the ejaculation lasted so long.
Why keep such a tag? Simple: to drown partners in pleasure. Uta was already something like his slave, but she was a child with zero tolerance for pleasure. Future encounters might involve opponents who wouldn't break from mere physical stimulation.
Having more tools was never a disadvantage. Still, even removing her pain, physical death remained a possibility.
"I should be careful when I use this. Ability Release…"
"Myohhh."
Removing the tag from his body was like popping an overfilled water balloon—the dam broke, and semen gushed out with a lewd squelch. Semi-solid, elastic fluid foamed as it refluxed through her vaginal and cervical openings.
"Aheh... Ahhhh!! Ahiii!"
Her legs splayed sloppily, body limp, Uta seemed to be climaxing repeatedly from the pleasure assailing her from within. Her consciousness must have been fading; her eyes rolled upward, unfocused.
She couldn't even breathe properly, merely twitching.
"Seriously, still coming out?"
Even as he observed, the cum continued to reflux without pause, already coating Uta's body thoroughly. It showed no sign of stopping.
"She's going to be insufferable when she wakes up."
He'd promised to fuck her however she wanted today, but she'd probably sulk over finishing after only one round. Slave though she was, she remained a child—mouthy and occasionally rebellious.
"Well, I'll let her have her fun again after she gets back from Elegia."
Luffy figured he'd make it up to her later.
'However, I had no way of knowing, while I was using my abilities to clean up the cum that had been ejaculated, that I would not be reunited with Uta in a few weeks after the expedition to Elegia ended, but in 10 years.'