Lets go! Training arc time!

After summoning Sasaki Kojiro, Sou brought him to meet Rayleigh. Rayleigh was rather wary, but he was confident that if he had any sort of bad intentions, he would be able to beat him. And since he realized that Kojiro had some skills that even he didn't have, he allowed him to teach Sou. Especially after he learned that Kojiro didn't know Haki and that he was way stronger than an average New World pirate even without it.

And so, Sou trained under both Rayleigh and Sasaki. Rayleigh took over training him in general battle, Haki, and everything else. On the other hand, Sasaki imparted his swordsmanship and all of his skills. On top of that, Sou gained a [Mission].

[Mission issued: Get stronger!]

[Requirements: At least 50% proficiency in each of Sasaki Kojiro's skills, and 25% proficiency in his ultimate technique, Tsubame Gaeshi. Gain an intermediate understanding of Armament, Observation and Conqueror's Haki]

[Rewards: 100 Summoning Points]

In the day, Rayleigh would train Sou's body, and add to his natural strength he gained from his father. He would also train Sou in Haki. That went... well.

"Alright, let's train your Observation Haki!" Saying this, Rayleigh brought out a wooden stick and a blindfold. Sou was blindfolded and forced to try to dodge the stick. He didn't do very well.

"Ow! Fuck! That hurts!" He said, getting hit again.

Rayleigh laughed and kept swinging. "Watch your language! And stop complaining and keep dodging." Sou tried, but he never got more than a streak of three dodges in a row, where he used his sense.

Later, they moved on. Sou, battered and bruised, was happy to move on. "Alright. How do we learn Armament Haki?"

Rayleigh gave a wicked smile. "You have to get hit by Armament, and try to activate it for yourself."

Sou just paled. "Shit," he said, fear evident in his tone.

"Language!" Rayleigh said, punching Sou in the stomach with an Armament Haki coated fist. And so, Sou got beaten up again. Multiple times.

Finally, they finished Armament Haki training. All that was left was Conqueror's Haki training. "Alright. I know you for sure have Conqueror's Haki, since both Roger and Rouge were incredibly powerful users of it. Since you haven't unlocked Conqueror's Haki yet, we'll have to try to activate it the more... forceful way," Rayleigh said.

Feeling a foreboding feeling, Sou tried to run away. It was futile, however, as he was blasted by a strong wave of Conqueror's Haki, immediately getting knocked unconscious.

And so, that same routine followed. Every. Single. Day. And to add to that, Sou also had training with Sasaki Kojiro during the night, which was horrible in a different way.

"Alright, the first skill we need you to learn is Vitrification, aka, 'the heart of clear water'. This will allow you to always keep a cool and collected heart. You'll also gain a certain degree of immunity to mental attacks. This is essential to eventually learn Presence Concealment and will help you learn everything else such as swordsmanship, Mind's Eye, and Knowledge of the Sowa. This might also help you in your Haki training, as Rayleigh told me that it relied heavily on the mind and spirit," Sasaki said.

In response, Sou smiled in relief that he wouldn't be beat up. "Alright, how do I get started?"

Sasaki just pointed towards a spot under the tree. "You just sit there and meditate. I'll be training over here. Once you can maintain a clear and empty mind no matter what, you will have gained the skill."

'Alright, that doesn't sound too bad,' Sou thought. Oh, how wrong he was. Even clearing his mind normally when meditating was incredibly hard. But it was even harder since Kojiro was training. His grunts and the sound of slicing were incredibly loud, and Sou was pretty sure he was intentionally increasing the difficulty, as sometimes Kojiro would slash down a tree near him and cause him to fear that he would be crushed. However, after he realized that Kojiro wouldn't intentionally harm him, he was able to concentrate a bit more.

And just like this, many days went by. Around three months after the start of his training, Sou made his first breakthrough, and many others quickly followed. After managing to keep a calm and clear mind no matter what Kojiro threw at him, Sou was given a System notification.

[Host has acquired skill of Assassin Sasaki Kojiro: Vitrification]

[Vitrification (B+) has been temporarily downgraded to Vitrification (D)]

[To raise Vitrification's level, Host must increase his proficiency]

At this, Sou's expression broke into a wide, gleeful smile. "Sasaki, I did it. I acquired Vitrification!" He told Sasaki.

At this, Sasaki returned his smile with a slight grin of his own. "Alright, next, it's time to learn Presence Concealment. Now that you know Vitrification, you should be able to learn this incredibly easy. While for most Assassins, it's an innate trait, this is instead a skill I learned myself. The basis of this skill is to completely cut off your presence and merge with your surroundings. To do this, just like Vitrification, you completely empty your mind, and cut off any sort of presence you might emit," he told Sou.

As Sasaki said, it was incredibly easy for Sou, as he was already used to the state of emptying the mind. He only needed to try for about an hour, before he was given a notification from the System.

[Host has acquired skill of Assassin Sasaki Kojiro: Presence Concealment]

[Prescence Concealment (D) has been acquired]

[Host can surpass Sasaki Kojiro and rank up Presence Concealment by further training]

However, this was not all. Now that Sou had Vitrification, his training with Rayleigh began to progress further also. Using the clear mind given by Vitrification, he was able to finally sense Rayleigh's presence and begin to dodge his attacks. At this, Rayleigh told him that he had officially acquired Observation Haki. Surprisingly, he was also given a System notification from this.

[Host has acquired the Personal Skill: Observation Haki]

[Observation Haki (D) has been acquired]

[It is possible to rank up Observation Haki by further training]

[Due to Host acquiring his first Personal Skill, Host has unlocked the Status window]

[The Status window only shows the Host's skills, as well as his proficiency in each skill.]

At this notification, Sou smiled contently, knowing he had finally acquired Observation Haki, and unlocked a new function of the System. Just like the acquiring of Vitrification, the acquiring of Observation Haki also lead to progression in other things. Namely, Armament Haki.

Now that Sou had found out the feeling of manipulating Haki, he was able to acquire Armament Haki after many arduous days of getting his ass beat by Rayleigh. Of course, he was given a notification for this also.

[Host has acquired the Personal Skill: Armament Haki]

[Armament Haki (D) has been acquired]

[It is possible to rank up Armament Haki by further training]

But even with the addition of all these different skills, they were still not Sou's greatest gain. It was, of course, the gain of Conqueror's Haki. Once again, because of Vitrification, Sou was able to gain Conqueror's Haki. His clear mind allowed him to barely endure Rayleigh's heavily weakened blast of Conqueror's Haki, and lash back out with his own, just-unlocked Conqueror's Haki. Just before he passed out from exertion, he was met with another notification.

[Host has acquired the Personal Skill: Conqueror's Haki]

[Conqueror's Haki (D) has been acquired]

[It is possible to rank up Conqueror's Haki by further training]

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A/N: Sorry if this chapter was a bit boring, but I felt it was necessary. However, the next chapter, while it will probably be mostly training too, will likely be more engaging, and more exciting. As always, put questions, concerns, suggestions, and worries in the comments.