Yoruichi's question carried a hint of threat, as she inquired whether Yuichi could indeed provide proof of being from the future.
With an air of nonchalance, Yuichi replied, "I could, but I'm having a hard time choosing what that something I tell you is. I don't want to affect the future too much or give you too much foreknowledge."
He then posed a request of his own, asking, "However, I must ask, if I give you proof, could you teach me something in return?"
Yoruichi chuckled at his request and responded, "If what you say really makes me believe you're from the future, I'll teach you any one thing."
A smile played on Yuichi's lips as he made his request, "I'd like you to teach me how to use Shunkō."
The prospect of learning such an advanced technique intrigued him, and he hoped to slowly get closer to her little brother Yūshirō and learn from him, however circumstances had changed and this was most likely his best shot at learning the technique.
"H…how did…", said Yoruichi but she was cut off by Yuichi who in a calm and composed manner, Yuichi explained, "How did I know about a technique that you're still perfecting and haven't taught anyone except for Yūshirō? The only way I could know about it is if I've seen you use it in the future. I hope this is enough for you."
Yoruichi's demeanor softened as her reiatsu receded, and she appeared deep in thought as she absorbed his explanation. After a moment, she nodded, conceding, "Fine, it seems you've managed to convince me, Yuichi. It's not easy to explain your knowledge of something that I've kept secret even from Suì-Fēng unless you've seen it yourself. Very well, as promised I will teach you the basics of Shunkō."
"The basics? You're not going to teach me everything you know about the technique?" asked Yuichi
Yoruichi shook her head as she answered, "No, as with when I taught Yūshirō anything else besides the basics I teach you will be a hindrance. This technique is a bit special as it manifested differently elementally for him as opposed to myself. So he could not use any of the attacks I developed and had to make his own. If afterwards you're able to use it, and if it manifests in a manner similar to mine, only then will I teach you more. If it manifests as something else then you'll have to learn on your own."
Understanding her reasoning, Yuichi nodded and replied, "I appreciate your willingness to teach me even the basics of Shunkō. I'm looking forward to learning."
Yoruichi smiled and moved closer to Yuichi. She began to explain the fundamental principles of Shunkō, detailing the process and its connection to one's reiryoku control. She explained that once reiryoku tansforms when using kido and the words help the reiryoku take form as spells. Shunkō uses that same process, but rather than a specific transformation you allow your reiryoku to enter a half-transformed state turning it into pure kido energy. Once you can form this energy you can then apply it to your fist or even your blade and that is Shunkō. She then demonstrated a simple version of Shunkō, allowing Yuichi to witness the unique way it manifested for her as lightning.
She instructed him, "Now, focus your reiryoku into your palm and attempt to achieve the half-transformed state I just explained. As the energy gathers you'll feel an intense pressure building up. Your body will want to instinctively want to release it, but you'll need to control it and keep it from escaping. Once you can hold it in your hand try to manually transform it as you do when you use kido."
With her instructions in mind, he focused his reiryoku into his palm, attempting to attain the half-transformed state that was the essence of Shunkō. As the energy gathered, he felt the intense pressure building up. It was a sensation he had never experienced before, akin to a tightly coiled spring. Yuichi's body instinctively wanted to release it, but he remembered Yoruichi's guidance about controlling it.
With ease, he held the reiryoku in his palm, resisting the urge to let it escape. This was quite similar to the technique he already practiced daily so it was easy. The true challenge, however, was to manually transform it, as Yoruichi explained. Although he had used kido many times and even created his own unique kido, he had never paid attention to how his reiryoku changed when he used the spells. It was impossible to change it if he had never felt what it was like when changed.
So Yuichi released the energy and allowed his attempt to end in failure. Yoruichi who had watched him sighed as she said, "I was surprised with how well you could control your reiryoku but it seems the transformation part is still too difficult for you. Keep practicing and eventually, you'll get it. However, you must only practice it here and never outside this room as it is dangerous. Do you understand?"
With humility, he accepted her advice and guidance. Yoruichi's admonition regarding the potential dangers of practicing Shunkō was well-received, and he nodded in understanding. "Yes, Lady Yoruichi. I understand and will follow your instructions diligently. I'll practice only within this room."
"Good, then I'll head off so you keep practicing. I heard from Kisuke you come here every day so I'll stop by in a week to check on your progress," said Yoruichi as she stood up, exited the osen, got dressed, and left.
With Yoruichi's parting words, Yuichi watched as she left the osen area. As she departed, Yuichi's focus returned to understanding what kido energy felt like. To do this he kept reciting the Shō incantation and using the spell to explore the changes in his reiryoku as he cast it. With each attempt, he paid close attention to the sensations and shifts within his own spiritual energy, seeking to grasp the transformation process that was crucial for Shunkō.
"Hmm, I can't see much, maybe I need to use a stronger kido spell, or focus more on the reiryoku. The changes could be so small one might not notice since the body automatically does it," thought Yuichi out loud.
With that in mind, he decided to try a stronger kido spell, believing it might provide a clearer sense of the reiryoku changes. He recited the incantation for a more advanced kido, "Byakurai," and released it with precision. As he did so, he paid even closer attention to the transformations occurring within his reiryoku. The goal was to see if the more powerful kido would create more distinct shifts in his energy.
The intense electrical energy of the Byakurai spell coursed through him, and Yuichi used this as an opportunity to attune his senses to the reiryoku dynamics in a more pronounced manner.