Niko thought for a while before responding to Yuichi's request. "It's technically possible to create a device like that, one that can activate and maintain a protective barrier without the need for constant focus. However, such a device might not be very practical. The way it would work is by drawing reishi from the air, but that presents limitations. The amount of reishi in the air may not be sufficient to create a powerful or long-lasting barrier."

Yuichi, always quick to come up with solutions, suggested an alternative. "What if, instead of pulling reishi from the air, we designed it to be a receptacle for reiryoku? We could insert reiryoku directly into the device and use that as a potent power source."

Niko considered Yuichi's idea but pointed out a challenge. "Creating a device that can store reiryoku is a complex endeavor, and I'm not sure how to begin building such a thing. Captain Urahara might have the knowledge and expertise for such an invention."

Yuichi, undeterred, proposed another option. "What about using a similar principle, but with reishi instead? Could we make it so that the device can gather and store a large amount of reishi, ensuring that it has an ample power source for the barrier?"

Niko nodded in agreement with this approach. "Yes, we can design the device to work with reishi, which would be more efficient. However, the challenge would then be quickly gathering a substantial amount of reishi to maintain the barrier effectively."

Yuichi smiled, displaying his determination, and said, "Let's go with the reishi-based approach for now. We can work on brute-forcing the problem. Having a working device, even if not elegant, is better than having nothing at all. We can refine it and seek a more elegant solution in the future."

Niko reluctantly accepted the compromise, recognizing the need for practicality. "Alright, we'll design it to gather and use reishi for now. I'll work on the modifications when I have free time since it’s interesting." She then brought over a blank paper and began outlining the device and possible components they would need.

After Niko finished the diagram she said, “Well this should theoretically work as we planned but there’s good news and bad news. The good news is I should be able to get most of the things we need to build it. The bad news however is that there’s only one place I know which would have the storage part that we’d need for storing a large amount of reishi. The Dark Society.”

Yuichi raised an eyebrow at the mention of the Dark Society, a place he had never heard of in the stories. Since the story mainly focused on Ichigo and his experience you rarely ever knew much about the Soul Society, Human World, and Hueco Mundo. It was at moments like this that Yuichi felt his knowledge was severely lacking.

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Niko clarified, "Yeah, it's an underground market known as the Dark Society. They traffic in various forbidden and unusual goods, including things like captured hollows, unregistered souls, gigais, and even passage into the human world. The tricky part is that they operate on a barter system, and the item we need for the reishi storage may not be easy to obtain or trade for with our current resources."

Yuichi considered this information and nodded. "I see. The Dark Society does sound like a rather challenging place to navigate, especially if we need something that's not commonly available. So from the way you talk about it, I’d assume you’ve been there and bought some things. What did you use as currency."

“Yeah, but I only ever bought small things, so I could always barter with the items I invented but no longer needed,” Niko responded, providing an explanation for her previous comment.

Yuichi acknowledged the importance of what Niko had revealed. He grasped the significance of the barter system within the Dark Society and the necessity of offering something valuable in exchange for the sought-after reishi storage component.

"Understood," Yuichi replied. "So, we require a substantial trade to secure the reishi storage component. We'll have to identify something of value that they would be interested in. Meanwhile, I'll head back and brainstorm potential trade items, and you can focus on completing the modifications for the tracker. Please inform me once you've determined the date of the next Dark Society auction. I'll devise a plan to acquire what we need."

“Agreed, just promise me you won't engage in anything overly perilous, alright? I'll inquire around and should have a date by the end of the week at the latest," Niko assured him.

"Very well, thank you," Yuichi replied. "I'll make my way back to my dorm now." He took his leave, leaving Niko to continue her work on the tracker.

Upon returning to his room, Yuichi cast a sound-blocking kido barrier to ensure privacy. He paced back and forth while pondering what they might offer for trade. "The only thing that comes to mind is having Miel use her ability to control hollows and procure a few. But I don't know when she'll return, so that's not an option. If I approach Urahara for assistance in constructing the device, he'll inevitably inquire about its purpose, and that's something I can't reveal. For now, let's focus on training. Maybe it will help clear my mind."

The following hours were spent in diligent practice as Yuichi delved into his training. He honed his control over reiryoku and reishi, fully immersing himself in his exercises. As Yuichi dedicated himself to his training and engaged in meditation within the confines of his sound-blocking kido barrier, inspiration suddenly struck.

A new idea began to take shape, one that centered around the potential value of his kido spells. Recognizing that neither he nor Niko possessed inventions for trade, an alternative path emerged. They could offer something distinct and highly valuable: original kido spells. The sound-blocking kido barrier he had just created served as a prime example.

Contemplating the possibilities, Yuichi realized that he could develop more original kido spells, ones that did not yet exist in the known world of Bleach. This notion held promise for a successful trade within the Dark Society, an underground market where unique and unconventional items were often in high demand. Yuichi's creative abilities could potentially shine through in the creation of such kido spells, providing them with the bartering leverage they needed. However, he decided to avoid spells with modern bases, like a kido spell for wiretapping a room, as they could be used against him.

With this new plan in mind, Yuichi continued his training with renewed purpose. His thoughts became laser-focused, and his skills improved significantly as he delved deeper into his training.