After the Straw Hat Pirates leave their shores, Vivi and Pell work together to make themselves stronger. Could be considered a sequel to 'Secession', but it also stands alone.
It was their daily training session. Every day they worked at rebuilding the country: Organizing irrigation crews, distributing aid packages to the starving masses, and sometimes just shifting stone and mortar. They were the symbols of the country's new future. He was the nation's Guardian Spirit, the watchful hawk who guarded each of them. She was the nation's pride, a shining beacon pointing the way towards a better tomorrow.
And so every day they toiled to pull the nation back onto its feet. But at night, when they were done and could fall away from the public eye and return to the walls of the castle, they trained.
Pell ducked under a horizontal slash, and parried a blow from the other slasher. The wire wrapped around his blade, locking into place. Pell grinned, then gripped his sword tightly in both hands and pulled on it. Vivi stumbled forward, pulled along by her own weapon, and Pell took advantage with a rising kick to the jaw.
Vivi cried out and fell backwards onto the floor. Pell followed through on top of her, straddling her and bringing his sword crashing down in a stabbing motion.
For a moment, the only sound in the darkened courtyard was their heavy breathing as they stared at each other. Then Pell stood, pulling his sword out of the sand he had embedded it in, centimeters from the princess's left ear.
"Remember," he said as he turned away from her and sheathed his weapon, "your Peacock Slashers are a unique weapon. Their malleability and wrapping capabilities make them nearly impossible to defend against. But those same features also mean that you must maintain pin-point control at all times, or you will open up a hole in your defenses that your opponents will be quick to take advantage of."
Vivi pulled herself back up to her feet, rubbing her jaw. That kick had smarted. She would have to make sure she got him back for that. She leapt forward, and Pell whirled, pulling his blade out of its sheath, and they met once more.
The palace staff often wondered about them, and why they trained so hard, and with so much fervor, but the answer was quite simple: they both wanted to become stronger.
Vivi knew that one day, the reconstruction would be complete, and the country would be able to stand on its own two feet again. And on that day, she would leave again, to find Luffy and his crew. This country was her treasure, and she would fight and work to defend it, but once it was able to stand alone, without her help, her heart truly belonged to her ocean-going nakama.
And when that day finally came, Vivi wanted to be strong enough to sail with them. They had been so monstrously strong when they had left her behind, and they were sailing into the heart of the Grand Line, the world's most dangerous sea. They would be growing stronger still by the day.
She knew they would accept her back no matter how strong or weak she was, but she did not want to be a burden. When she rejoined them, she wanted to be able to stand shoulder-to-shoulder with them as they face down their challenges.
Pell still felt the sting of shame from his defeat. He was supposed to be the country's protector, but when a threat had at last appeared, he had failed miserably to defend against it. Miss All-Sunday had gone through him like a sheet of paper. It mattered not a bit to him that Chaka and Igaram had been similarly defeated, or that he had been up against a foe too powerful to hope to defeat. If he was to defend this nation, he needed to be stronger and faster than everything that waited beyond its borders.
And so they trained.
Their weapons came crashing together with the sound of steel on steel. Vivi whirled, swinging her Peacock Slashers in wide circles again and again, bringing them down onto Pell's sword again and again.
"Come on, don't hold back on me!" Pell shouted as he effortlessly parried her blows, "You can do better than this!"
He was absolutely correct. Vivi had been using that weak attack sequence as a setup for a special technique. She'd been practising this one for weeks, keeping it a secret so she could surprise her mentor with it when she was ready. And now...
"Peacock Slasher..." she called out as she struck out with both weapons, cracking them like a whip. They wrapped around his sword and gripped it tightly, much like before, only this time she was in control.
"...Disarm!" she finished, pulling sharply in opposite directions with both Slashers. Pell's jaw dropped in shock as his sword was twisted out of his grasp. He reached out to try and grab it, but Vivi whipped it out of his reach and sent it flying before she released it.
She swung her weapons forward, bringing them to just below his throat. He froze. She had won this round.
Vivi released him, and he walked across the courtyard to retrieve his fallen weapon.
"Good," he said with a ferocious grin. "Again!"
And then they were sparring again, and it lasted well into the night.