So, I was going to go to sleep, because it's seriously late and I haven't gotten much sleep lately, but then this story I've been playing with for a bit suddenly started taking proper form in my brain, and I had to write it down before I lost it. I hope you enjoy this which I sacrificed my sleep to give you.
On a normal day, Zoro could beat Luffy in a fight. He was physically stronger. Even before haki, swords had been able to hurt the rubber body, and still they gave him an advantage. He had always been quicker to strike, his bloodlust more prominent, his hesitation more easily put aside. Of course, on a normal day, he would never consider fighting his captain, but he knew he would win if he did.
He also knew Luffy could beat enemies against whom he stood no chance.
On a normal day, Luffy would always hesitate before striking a friend. On a normal day, he would always pull his punches. Not by choice, but he would never, ever be able to use his full power on someone he liked. His power was tied to his level of determination, and he could never be determined in a fight where his enemy was someone he thought was nice, much less a comrade.
Zoro had seen him fighting Usopp. Had seen his eyes filled with nothing but hurt and hesitation. Had seen how, later, Luffy had had problems with enemies he could at least have rivalled on a normal day.
Zoro had seen him fighting full-power too. Seen him fighting against enemies for whom he had no sympathy. Enemies he needed, and wanted, to fight. He had seen the pure strength of determination in those eyes, and he knew that the power behind those eyes was one he could never stand against.
On a normal day, he never would.
This was not a normal day.
The puppet puppet fruit was one of the stranger fruits they had met. By the time they were told how it worked, it was already too late. Zoro was the first to fall to the touch of the little man as he passed the on the street, and not a one of them noticed.
One by one, their bodies had been replaced with puppets identical to themselves, their minds trapped inside, parasitized and powerless. The puppets leeched on their memories and personalities, mimicking them perfectly, secretly being under the enemy's command. Zoro could only watch helplessly as he felt his new puppet-body going through the motions he would always go through. Sleeping, drinking, fighting the cook, walking around while everyone else got themselves lost, finding his way back. He could tell the puppet even found its way through the streets and between the trees the same way he would have, by picking a path and relying on fate to guide him, but with all his strength of mind he could not move a single finger.
When the cook was taken, they kept up the fights. Spouting insults at each other and trading familiar blows, but it was nothing but a puppet show. All a perfect puppet show. Zoro had never felt so helpless. Even after losing to Hawkeye, lying on his back, unable to move, swearing to never lose again. Even then, there had been power in his words and in his heart.
Only Nami, Usopp and Luffy were left and ignorant, and Zoro wondered how the touchy-feely captain had avoided it, when a villager boarded the ship in the middle of the night. He explained that the entire island was under the control of the puppet master, a sadistic man who made pirates fight their own friends. He explained that he was freed because he, or his puppet, had fallen off a cliff and broken his neck, and with the puppet broken, his real body had returned. He explained how to recognize puppets by a near unnoticeable tick, and the three remaining crewmembers had looked at their comrades and turned tail.
Zoro's puppet had smiled then, a predatory smile, and it had gone into the streets, hunting. He had felt the familiar rush of bloodlust through the unfamiliar body. So powerful, so right, and so wrong. So horribly misaimed.
Soon, he had heard Nami scream, and later her mocking voice and the whimpering of Usopp. He could sense his captain, the one he had sworn to defend and serve. He could sense his fear. He could sense his fear fading, and giving way to something else. And then he could sense that endless determination.
One by one, the presences of the puppets were broken. The smallest first. Quickly, painlessly and effortlessly. The cook had come to Nami's aid, the puppet following his basest instincts. Leaving himself open for attack. Somewhere in between, the puppet master fell. Almost an aside, just to make sure he never touched anyone again. Robin took a while. She was intelligent, her puppet was intelligent, but his instinct was too powerful to trick, and the puppets were not instructed to work together. Franky took down a whole row of houses, but he fell relatively easily. Brook was fast. Not fast enough.
Then there was only him. The village had gotten itself lost. There were only trees now, but he knew Luffy would find him.
His need, the puppet's need for battle flared at the sight of the hatted man in front of him. The vicious smile of the green-haired beast met the unsmiling expression of the scarred, elastic monster. The others had mocked and taunted that he could not seriously fight his friends, and he had answered that they were not, and that they should give him back his real friends, but between these two, not a word was uttered.
On a normal day, Zoro did not fear. He did not fear enemies a thousand times stronger than himself. He did not fear the chaos or the creatures of the ocean they sailed. He did not fear death.
On a normal day, even his comrades in trouble did not scare him, as he knew the captain wove his own fate, and it was a fate he trusted completely.
This was not a normal day.
This was the day those eyes and the power behind them, the one he had sworn his life, his honour, and his dreams to, turned against him. This day, Zoro feared.