In one piece world
As it happened in the canon story, the Straw Hat crew beat up the Celestial Dragon members, leading to Admiral Kizaru and other Marines chasing them.
At that moment, Bartholomew Kuma appeared and sent them to various islands to ensure their safety. Given Chopper's tendency to panic, Kaoru had to calm him down.
Surprisingly, Chopper managed to resist Kuma a little, perhaps due to their adventures in the shinobi world for over two years.
Today, Chopper sent a message to Kaoru, stating that the leader of the Whitebeard Pirates' second division would be executed. This person was Ace, Luffy's sworn brother.
With the anticipated plot unfolding, Kaoru couldn't stay idle. The opportunity to show off had arrived, and Kaoru immediately prepared to go to the world of One Piece. There were rabid dog and other animals that needed to be dealt with.
Without wasting much time, Kaoru's preparations were complete. He ordered a few jars of Puni Jelly, Rasen pudding, and various healing items from Ryza. All materials were provided by Kaoru himself.
He also didn't forget to buy Sea Stone handcuffs to deal with Devil Fruit users.
After ensuring his preparations were ready, Kaoru used his world-traveling ticket. In an instant, Kaoru was enveloped in a blinding white light and disappeared from the guild's aura, heading towards the world of One Piece.
-------
In one location in East Blue, on a giant bridge known as Tequila Wolf.
A woman with long black hair and a very beautiful face was currently being captured and shackled by several guards.
Despite the unfriendly weather and environment, the woman still looked elegant, as if stating that even if thrown into a pile of garbage, a diamond would always be valuable and have worth.
However, this time, the attention of all Tequila Wolf residents, guards, and the woman was diverted by something.
They saw a strange circle followed by a gleam of light that forced them all to close their eyes.
After the light subsided, they could all see a human figure emerging from behind that light.
A very beautiful woman, with hair mixed between black and white, truly beautiful. Even for the woman, she felt that her beauty would be overshadowed when compared to the newcomer.
The figure looked around with a puzzled and curious expression but was surprised when seeing the woman in shackles.
She smiled friendly, as if meeting a long-lost friend. Everyone was stunned when they saw that smile, but the words and actions of the figure surprised them even more.
"Hoo! Random teleportation is interesting. I didn't expect to meet you, Nico Robin! Chopper has told me a lot about you, you know. In that case, let me help a bit!"
The figure was Kaoru, and simultaneously with that, Kaoru snapped his fingers, and in an instant, all the guards began to behave strangely.
Their bodies vibrated followed by screams, and in a very short time, their bodies crumbled as if crushed by something unseen, disappearing without leaving a trace, as if they never existed in the first place.
All Tequila Wolf residents were frightened when they saw the power demonstrated by Kaoru. As he approached Robin, the residents also slowly retreated, but one brave little girl stood in front of Robin, facing Kaoru.
Kaoru, seeing this, immediately put on a friendly face and tried to persuade the little girl.
"Calm down, little girl. I'm a friend of the older sister over there. Let me give you something!"
Kaoru immediately took out some food and gave it to the little girl. Although initially scared, after seeing Kaoru's face not showing any evil intentions, she accepted it.
The residents briefly envied that the little girl got free food, but with Kaoru's presence, they gave up any malicious intentions.
On the other side, Robin, who was helped by Kaoru, lowered her suspicions when hearing Chopper's name, as only their crew knew how close she was to Chopper.
"Firstly, I thank you for helping me. Um - miss?"
"Kaoru. My friends usually call me Kaoru. Ah, and one more thing, I'm a man!"
"...."
"...."
"...."
"EHHHHHHH!!!!!"
The silence that momentarily emerged vanished due to the shocked screams of the residents upon hearing that Kaoru was actually a man.
"Hahaha, no need to be so surprised. Also, I came here to help the Straw Hat crew, and if you all want, I don't mind taking you out of this place. So, if possible, please discuss it with the other residents while I talk to my friend here!"
Hearing the news that Kaoru could take them away from this place, they were all surprised. They quickly informed other residents and discussed the offer Kaoru made.
The reason they didn't doubt whether Kaoru could do it or not was because of the performance he had shown earlier. The residents had been on this bridge for over 700 years and never knew about the outside world. With Kaoru displaying his power, it's no wonder they considered him a god or a god's envoy.
Kaoru, seeing the residents starting to leave, looked towards Robin and said.
"Saa, Robin-san, considering what happened to you all, I'm sure you know what to do, right? If so, I'll give you a choice."
"What is it?"
"First, I can send you to meet the other Straw Hat crew members. Second, I can send you to the Revolutionary Army, and you might be lucky if you stay with them until the chaos in Sabaody subsides. Third, you can join me, and I will train you to become stronger."
Hearing the options provided by Kaoru, Robin pondered, weighing the pros and cons of each choice.
The first option was, of course, excellent. With it, their crew could reunite and continue their journey. But then what? Robin could imagine their crew dying right away after reaching the New World if they continued their journey now.
Then the second option, which seemed a bit suspicious. Why the Revolutionary Army? She didn't know anyone there, and Robin was slightly suspicious that Kaoru might be a member of the Revolutionaries and if the guess is wrong then what? she will be left alone again.
Finally, Robin didn't know why Kaoru offered that option, but as someone who survived being chased by the Marines, Robin understood that Kaoru had no malicious intent.
Robin was also very sure that if given the chance, Luffy would undoubtedly choose the third option. Because right now, they realized that their strength was nothing compared to the monsters in the New World.
Moreover, even if Kaoru had bad intentions, he could destroy Robin's body like what happened to the guards or capture her and hand her over to the World Government without much question.
Deciding her choice, Robin looked at Kaoru with determination.
"I beg you, Kaoru-san! Please teach me to become stronger!"
Robin, a survivor who wanted to continue adventuring with her comrades and learn about the Void Century, didn't hesitate to do so if bowing her head and pleading could make her dreams easier to achieve.
"Good choice!"
Kaoru looked around and decided that the extreme conditions in Tequila Wolf were perfect for enhancing Robin's basic abilities, so he chose to start her training here.
"For security matters, don't worry! I've set up a strong barrier to send Uranus's attacks back to Imu's house, so please tell the residents to think carefully about their choices."
Robin didn't understand about barriers or anything like that, but hearing the mention of one of the ancient weapons, Robin felt relieved. She also didn't feel that Kaoru was lying, which is why she hurriedly went to inform the residents.
--------
Several days passed very quickly. Kaoru, relaxing in a chair, reading a newspaper while enjoying hot chocolate, managed to get information about the execution of the Whitebeard Pirates' second division commander scheduled for this afternoon.
Knowing that, Kaoru immediately looked at Robin, who was still running out of breath in the extremely cold weather without wearing warm clothes.
Kaoru understood very well that using Haki required a strong body and soul, so he deliberately forced Robin to surpass her limits.
Moreover, Kaoru didn't need to worry. As long as Robin didn't die instantly, he could heal any wounds or illnesses as severe as possible with various techniques and supplies he had.
"Robin!! Today's training is enough; you can rest!"
Hearing that, although feeling happy, the exhaustion Robin felt prevented her from commenting, and she just obeyed to rest.
She immediately fell into the pile of snow and was then helped by the little girl named Soran, who had confronted Kaoru earlier.
"Soran-chan, please take care of your sister Robin, okay? Just give her the medicine in the cabinet; she'll recover instantly. I'll be going for a bit. If you want, you can watch this!"
Kaoru handed her a Dendenmushi and connected it to Morgan's channel broadcasting Ace's execution.
Without waiting for a response from Soran, Kaoru immediately opened a portal and entered it.
On the other side, a few kilometers above the sea surface, a portal appeared, and Kaoru emerged from it.
This time, Kaoru was right above Marineford. He could witness the battle between the Marines and the Whitebeard Pirates' fleet.
A scene that once made him shiver due to the tension of that arc.