The Chain of Causation was the term that describes the sequences of events that make up cause and effect. It is the set of links binding together actions and their consequences into a coherent and sensible narrative. Even in the logic-deficient Grand Line, the Chain of Causation allowed people to make some kind of sense of the world, even if it wasn't the vaunted 'common' sense.
Even an utter blockhead like Monkey D. Luffy was capable of stringing together cause and effect.
Normally, Luffy only had to care about the simplest of causes and effects, such as punching people in order to hurt them. Forced to undergo repeated temporal resets because he simply could not keep his mouth shut eventually beat it through his rubbery skull that blurting out that he was a time traveler always ended badly. Either he scared off his nakama because they didn't yet trust him enough to simply take his words at face value, or he attracted the attention of people he wasn't yet strong enough to fight.
This discovery was made mostly by accident, because he simply got fed up of repeating himself. As soon as he stopped mentioning time travel, Kizaru stopped showing up. Even Luffy managed to connect those dots.
By that point, he'd already found the best way to move forward because of simple repetition. He knew the best way to become friends with Coby, get Nami to travel with him and convince Zoro to join his crew without something happening to immediately ruin it.
And the trick turned out to be really simple, he had just been in too much of a rush to get his nakama back and save Ace to do it properly. Tell Coby that it's up to him to chase his dream, tempt Nami with money and tempt Zoro with strong opponents.
"Are you here to collect the price on my head, you flashy bastards?!" Buggy the Clown yelled.
"That's right!" Nami confirmed with a big smile, already counting the fifteen million beli his head was worth. "Go get them, boys!"
This run through, Luffy had at no point mentioned being a pirate, allowing Nami and Zoro to assume that they were forming a bounty hunter group. It had worked really well for getting them to join his crew, but pretending that he wasn't a pirate was hard.
The only thing that was making it bearable was the certainty that it could never last. Luffy had declared war on the World Government to get Robin back and he would gladly do it again.
"That guy looks like a swordsman, I'll take him." Zoro said with an eager grin.
"Is that Roronao Zoro?!" Buggy recognized the man who used three swords. Quickly, he started aiming his big cannon. "Die flashily!"
Luffy stepped forward and used his balloon technique to deflect the Buggy Ball, scowling when the clown-themed pirate used his own crew as shields, just like he'd done the first time around. "I'll take Buggy."
The resulting fight was… easy. Luffy knew all of Buggy's tricks and was much stronger than he had been the first time. Zoro didn't get surprised by Buggy's Bara Bara No Mi and so didn't have to fight Cabaji with a stab wound in his side, and the acrobat was no match for him. Mohji the Lion Tamer and Richie the Lion didn't make much of an impact either.
"That's fifteen million and all the treasure in their hold." Nami cackled greedily. "Oh, this was a great idea. I should have made a bounty hunting group sooner."
"It's not your bounty hunting group, witch." Zoro said blandly. He would never sail under Nami. To having her as a crewmate he had no objection, but he would not have her as a captain.
"Shut it! You and Luffy said I could have 95% of the money!" She hollered at him.
Which they had. Neither of them two men cared about money, so they hadn't tried very hard to haggle with her.
Frankly it didn't sit well with him to turn anyone over to the Marines. Buggy and he had been… not friends, but allies when he'd last seen the clown pirate. They had gone through Impel Down and to Marineford together. He knew that none of that had happened because of the time travel, but it wasn't something he could easily forget. Still, his crew was more important.
They went to talk to Mayor Boodle and the Marines were called. It took them the better part of two days to arrive, but they picked up the Buggy Pirates without issue. In fact, they were downright happy to see them again, as the Marines were from Shells Town and still grateful to them for getting rid of Captain Morgan. With them not being declared pirates, they had left the place on good terms.
Unfortunately, the delay caused by waiting for the Marines meant that Captain Kuro had enough time to enact his plans. By the time they got there, the Gecko Islands were in a state of mourning, as the rampaging Black Cat Pirates had killed quite a few people, including Kaya, Merry and Usopp.
Enraged at the loss and at himself, Luffy beat Kuro to death without explaining to anyone why he was attacking the butler-turned-lord. Then he went to sleep, hoping that that mysterious time travel still worked.
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After losing Usopp because they were too slow, Luffy did something he really disliked doing. He sat down and thought.
When remembering his adventures, he'd always focused on the excitement, the people he'd met and the cool stuff he'd seen. This time, he tried to remember how often he and his crew had arrived somewhere just in the nick of time.
The answer turned out to be… a lot.
Zoro, Nami, Usopp, Sanji, Vivi, Chopper and Robin would all probably die if he didn't get to them quick enough. Franky and Brook were the only ones that weren't in immediate danger. That took a lot of fun out of the adventure and instead made it a stressful race against time.
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"Are you bounty hunters?" Lieutenant Ripper asked after Captain Morgan was taken down.
This was the point where, in the last run, Luffy had sucked in his lips to prevent himself from blurting out the truth and instead let Nami's greed run wild.
"No, we're pirates." He declared this time, with both pride and relief.
"What?!" Nami screeched. "You never said anything to me about being a pirate!"
Zoro was also a bit surprised, but shrugged it off. He didn't care what he was, as long as he remained a swordsman.
"Because you wouldn't join my crew if I did." Luffy complained.
And that was how he learned once again that being honest at the wrong time could end badly. After that, Nami wanted nothing to do with them even when they ran into her later, because she felt that she had been tricked. The run reset before they made it to the Gecko Islands.
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Try as he might, Luffy simply could not convince Nami to join his crew if he told her that he was a pirate. And if he let her think that they were setting out to be bounty hunters, then he could not convince her to keep going without collecting on Buggy's bounty. He could order it, as the captain, but she resented it and left the crew immediately so that she could collect by herself.
He knew that Nami would eventually get over her hatred of pirates and put her nakama before her greed, but that wouldn't happen until the saw-nose bastard got his ass kicked, which wasn't going to happen until after they recruited Sanji.
It was a conundrum that was making his poor brain hurt as he tried to puzzle it out.
Eventually, he gave up on trying to get Nami to join his crew right away. He remembered that during the first run, he didn't encounter her until he and Zoro got to the town that Buggy was wrecking. As much as it burned him to know that she was right there, he decided to see if he could recreate the circumstances of their first meeting.
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Nami and Luffy's first meeting came about when she was being chased by three of Buggy's crew members and got inadvertently saved because the rubber man finally got himself free of the big bird that had him in its beak.
Any reasonable man will tell you that this is not a set of circumstances easily repeated, especially when the one attempting to do so barely remembered what had happened.
After beating up Captain Morgan and recruiting Zoro, a process that Luffy had streamlined through trial and error to take as little time as possible because he hated repeating the same boring stuff over and over, the two of them hastily prepared and set out to sea.
Alas, both were horrendous navigators and changes in their time of departure, as well as Luffy's own mentality, meant that the short voyage didn't go the same way. Luffy's luck was absurd, but it wouldn't bend reality if he tried to get the same results with different actions. They got lost at sea several times.
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"AAAAAAARRRGHHGFAAAARGH!" Luffy roared unintelligibly, once more back on his little dinghy drifting slowly towards a familiar whirlpool.
Enraged, he smashed his fists against the little boat and broke it. As he drifted down into the depths, quickly drowning, only one thought went through his mind.
I need a navigator to get a navigator?!
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"Hey, Coby, could you come with me and Zoro to the next island? We need a navigator."
"I'm sorry, Luffy, but I can't associate with pirates anymore."
Coby was apologetic, but firm. He had his own dreams to chase and Luffy could not bring himself to endanger them.
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"Hey, Coby, could you come with me and Zoro to the next island? Our navigator is on the next island and Zoro and I don't know how to get there."
"Eh?" Zoro made a noise of protest. "It's to the north, isn't it? That means we just have to go up."
Coby goggled at the swordsman's nonsensical reasoning, but still regretfully shook his head.
"I'm sorry, Luffy, but I can't associate with pirates anymore."
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"You could come with us to the next island." Luffy suggested. "Our navigator is there and I heard that Buggy the Clown is causing trouble nearby. If you turned him in and asked to join the Marines, they'd be happy to take you and we wouldn't get lost at sea."
Zoro looked interested in the information, but Coby turned pensive. "You really think that would be better than just enlisting right here?"
"They'd have you mopping floors." Zoro pointed out. "But if you brought in a bounty, you'd get a head start on your career."
Luffy no longer felt bad about doing this to Buggy. It had only taken one run where they managed to eventually make it to Orange Town, only to see what he and his crew had done to Nami when he wasn't there to save her to cure him of any good feelings he had for the clown pirate.
He felt worse about tricking Coby like this, but asking nicely didn't work and they needed to get to Orange Town quickly. Luffy wasn't sure he could handle seeing what happened to Nami again if they didn't.
"Is it really okay for me to take credit for you beating up Buggy, though?" Coby asked nervously. "It feels dishonest."
"Just work extra hard to earn it." Luffy said.
The rubber man knew himself to be a terrible liar. He couldn't do it to save his life and it had already cost him several runs when he tried. Telling the truth had cost him even more runs. Through sheer, mind-numbing repetition, Luffy was being forced to learn how to be economical with the truth.
Coby thought about it for a while and then gave Luffy a firm look. "Alright, I'll take you and Zoro to Orange Town and your navigator, but I won't take all the credit for Buggy's capture."
"You'll be the best kind of Marine, Coby." Luffy smiled at his pink-haired friend.
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With the expertise of someone using the most basic of navigation skills instead of a random number generator or vague impressions based on current temperature, they made it to Orange Town with time to spare.
This also turned out to be a problem.
"You're no swordsman." Zoro told the felled Cabaji, disappointed by his performance.
Luffy, meanwhile, was standing over the defeated Buggy with a frown. Nami was nowhere in sight.
"Oi, Luffy, where is this navigator of yours?" Zoro asked.
"She should be close." The rubber man said, looking over the village.
They never did find her, because Nami was a skittish sort and hadn't survived so long by taking stupid risks. Risks like approaching obviously dangerous individuals that she knew nothing about.
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Luffy disliked waiting, but he disliked repeating the same events over and over even more.
"Luffy, why are we hiding on a roof?" Coby asked, confused. "Weren't we going to find your navigator?"
"She's somewhere here." Luffy said, staring out across the town.
She had been here the first time around. She had to be here now, because if she wasn't then the only place he knew where to find Nami was on Alvida's ship at the very start of his adventure and he had already failed to recruit her there.
They waited for over an hour before it paid off. Shouts echoed across the empty town, the cadence of angry men screaming insults and threats. Occasionally, they also heard the higher pitch of a girl's voice, this one scared.
"Let's go!" Luffy yelled enthusiastically, glad to be doing something. He grabbed Zoro and Coby with his rubbery limbs and launched himself in the direction of the screams.
"No, wait!" Zoro and Coby protested before they went airborne.
But Luffy was not in a listening mood. He was hopeful that this would be the run where he finally succeeded in getting Nami to join him. Plus, he was hungry.
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Nami was running for her life and genuinely afraid that she wasn't going to get away this time. Stealing from pirates was always dangerous, but usually she was able to do it while they were distracted. This time, she'd overestimated how distracted they were.
And then there was a thunderous crash and pained yelling from behind her. Despite knowing that it would be better to keep running, she couldn't help her curiosity and looked back.
The three unwashed idiots that had been waving sabers at her were groaning on the ground, along a green-haired man and a pink-haired kid. Standing over them all was a dopey-looking black-haired teenager with a straw hat and a big smile aimed at her.
"Gonna… cut him up." The green-haired man grumbled painfully, getting on his feet. She saw the three swords at his waist and tentatively identified him as the notorious bounty hunter Roronoa Zoro.
"Hi!" The straw hat guy greeted, with every sign of being happy to see her.
"Hello?" Nami returned cautiously. He had saved her, but something about this guy was weirding her out.
"Luffy, is she the navigator you mentioned?" The chubby pink-haired kid asked.
"How did you know I was a navigator?" Nami demanded sharply.
"I know stuff." The apparent Luffy said, his smile disappearing into a more neutral look. "Come join my crew. You can be in charge of the treasure."
Nami's greed almost made her agree to that very tempting offer, but she hadn't been born yesterday and this was too suspicious.
"Umm, I think I'll pass." She said, nervously backing away and preparing to run. "Thanks for saving me, but I think I'll just go…?"
Her statement ended in a questioning lilt, because she was expecting anger or threats, but Luffy just looked at her.
"Oi, Luffy, I thought you said she was waiting for you?" The green-haired man asked.
"We won't hurt you, Nami." Luffy said, ignoring his friend and continuing to stare at her.
"Good to hear, see you later." Nami said in a rush and speedwalked away, expecting to be chased again at any moment.
"What did I do wrong this time?" She heard Luffy mutter to himself in frustration.
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Nami was running for her life and genuinely afraid that she wasn't going to get away this time. Stealing from pirates was always dangerous, but usually she was able to do it while they were distracted. This time, she'd overestimated how distracted they were.
Turning a corner, she nearly skidded to a halt as she saw three more men in her way, but shouts from behind spurred her on.
A moment later, she identified the green-haired one with three swords at his waist as the notorious pirate hunter Roronoa Zoro. The other two didn't look that strong, but he would definitely be able to handle a bunch of nobodies.
Desperate plan decided on, Nami waved her hand at them and yelled. "Zoroooo! Three more pirates coming your way."
He didn't look surprised or confused, but his eyes sharpened as he called back. "Are you the navigator?"
How did he know I was a navigator? The navigator? Were they looking for me? Nami didn't think she was famous enough for anyone to know her, but also didn't have time to think about it right now. "I'm the best damn navigator you'll ever meet!"
A predatory grin split his face. "Good, get over here."
Nami needed no further invitation and quickly hid behind the swordsman.
"Hi!" The straw hat-wearing guy greeted brightly. "Welcome aboard!"
Eh? Had she just joined up with someone?!
"Get outta the way!" The unwashed idiots chasing her hollered. "That bitch stole from us!"
"If you can't hold on to it, you don't deserve to have it." Zoro said uncompromisingly and swung two of his swords. All three of her pursuers fell to the ground with cuts across their chests.
His attitude was something that Nami could get behind… when it favored her, of course.
"Thanks, I was in a pretty bad spot there." Nami sighed in relief. "I'm Nami."
"I'm Luffy!" The straw hat guy grinned widely.
"Zoro." Zoro grunted, confirming his identity.
"Coby." The small pink kid said shyly. "I'm not part of the crew, I just helped Luffy and Zoro get here."
"Crew? Are you bounty hunters?" Nami asked.
"Pirates." Luffy corrected. "Except for Coby, he wants to be a Marine."
Nami had just been gearing up to yell about how she was absolutely not joining up with any stinking pirates when he mentioned that last bit and derailed her thoughts. "What? If you want to be a Marine, then why are you hanging around pirates?"
"Well, umm…" Coby awkwardly scratched at his head. "I was an unwilling member of the Alvida Pirates for the past two years until Luffy saved me. I was going to join the Marines at Shells Town, but Luffy and Zoro are really bad at navigating and asked me to help them get here."
"I am not bad at navigating! I can't help it if the ocean moves around!" Zoro barked indignantly.
Nami could only stare at him. What? Of course the ocean moved around, it was made of water!
"A-anyway." Coby coughed, seemingly deciding that it was not worth arguing with the swordsman on the finer points of navigation. "I'll join the Marines after Luffy and Zoro beat up Buggy and we call them in to collect him."
Nami's soul cried out in pain at the thought of fifteen million beli going to someone else, but her opinion on Luffy softened considerably. Even if he said he was a pirate, he had helped out someone who'd been in a similar situation as her and was by all accounts a friendly guy.
Maybe staying with Luffy and Zoro for a while wouldn't be so bad? She would still keep her guard up, though.
"I guess I can be your navigator for a while." She said noncommittally.
"Alright, let's go kick Buggy's ass!" Luffy shouted, raising his fists into the air.
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