If you look at the plot later on, you'll see that while Kisuke and Yoruichi are indeed childhood friends, neither of them particularly cares for romance. Their minds were always occupied by other matters.
Kisuke Urahara approached Makiya suspiciously, his eyes filled with anticipation. "Did you bring the thing?"
"I brought it." Makiya pulled a USB drive from his robes and handed it to Kisuke.
Technology exists within the Soul Society of the Soul Reaper world as well, and it is remarkably advanced.
"I had to endure five drinking sessions with Captain Kyoraku to get my hands on this. How do you plan to thank me?" Makiya winked at Kisuke Urahara, his tone thick with teasing.
"Now, now, don't be like that. This is for our common cause, after all. Even if it took fifty sessions, you'd still have to drink. Once there's a result, you'll be the first I share it with," Kisuke said with a grin, adjusting his green-and-white striped hat.
He plugged the USB drive into the equipment behind him. Soon, the massive gate they had built nearby began to hum. In the center of the previously empty frame, a pitch-black fluctuation appeared.
A Senkaimon—a spatial gate capable of reaching the World of the Living or Hueco Mundo directly.
The USB drive contained operational data for the Seireitei's official Senkaimon. By using a machine to analyze this massive amount of data, Kisuke could ensure that the fluctuations from his privately built gate matched the official ones, effectively hiding it from prying eyes.
As the saying goes in the Seireitei, many rules can be bent as long as you aren't caught and don't harm the interests of the majority. As long as the Head Captain can save face, he'll usually turn a blind eye.
"The Senkaimon is stable. Come on, let's head to Hueco Mundo!" Pressing the final button, the black space in the center solidified. A flash of white light washed over the surface, and a Japanese-style sliding wooden door appeared. The doors slid open automatically, revealing a dark void and a straight, narrow path.
Kisuke claimed it was stable, but Makiya's gaze pierced through the doorway. He could feel the intense spatial fluctuations emanating from within; spatial turbulence was everywhere, like a hurricane whipping above the narrow path.
The various dimensions of the Soul Reaper world—the Human World, the Soul Society, Hueco Mundo, and Hell—are not directly connected. Instead, they are linked by tunnels that allow for the exchange of matter. The four great worlds are layered like massive spatial bubbles stacked upon one another, with spatial turbulence and all sorts of strange, magical creatures existing between them.
There are even countless small spatial bubbles floating within the turbulence. Makiya remembered that in the later parts of the story, there was a girl who could freely travel between these small bubbles, using the pockets of space floating outside the worlds as her personal safe houses.
That girl seemed to be a pink-haired twin-tail. She was quite cute.
"Tsk, it looks a bit unstable. Are you sure the Senkaimon is running normally?" Makiya peered inside, his voice full of distrust.
Kisuke Urahara had a typical scientist's personality; you could insult his character, but you couldn't insult his inventions. Facing Makiya's doubt, Kisuke expressed his stance through action. He took a step forward into the Senkaimon and stood firmly on the narrow path.
A faint white glow appeared on the surface of his body. It was Kisuke releasing his Reiatsu to resist the spatial turbulence.
"See? I told you there wouldn't be any issues," Kisuke said, turning back to Makiya. Because the spatial film on the surface of the Senkaimon blocked sound, Makiya could only judge what he said by reading his lips and the smug expression on his face.
"Coming, coming." Makiya followed closely behind, stepping through the Senkaimon and onto the path.
The two figures gradually vanished into the spatial tunnel.
After they left, the Senkaimon slowly closed, and the machinery stopped running.
Maintaining the Senkaimon required a massive amount of energy and made it easy to detect. Akane, who remained in the underground space, was responsible for guarding the gate. At the agreed-upon time, Akane would reopen the Senkaimon to bring back Makiya and Kisuke, who carried tracking devices.
She was already in the same boat as Makiya and Kisuke. If the nobles found out she had used Hollow powers to break her limits, Central 46 would never let her off. Therefore, she was someone they could trust.
Meanwhile, at Makiya's barracks, Soi Fon's face was flushed with frustration when she couldn't find him. She had thought her Captain had finally decided to be diligent for once. Recalling the kick she gave him the night before, Soi Fon felt conflicted, wondering if she had been too harsh. What other Vice-Captain would dare treat their Captain like that?
The Soul Society had a strict hierarchy. Born into a lower-tier noble family, Soi Fon strongly approved of this system of rank. Thus, she had gone to the kitchen to cook a pot of hot porridge, intending to apologize to Makiya.
However, when the tsundere Soi Fon pushed open the Captain's office door, she saw no sign of Makiya. An ominous feeling immediately took hold of her heart.
Sure enough, she approached the desk and looked down to see a note Makiya had left:
"To my cute, reliable, and hardworking Vice-Captain Soi Fon: As your Captain, I was crossing the street this morning when I saw a black cat sitting in the middle of the road. Consequently, I lost my way on the path of life. I'll be spending the next few days searching for the meaning of life. I'll leave the paperwork to you!"
"Ehehe!"
"Signed, Makiya."
After Soi Fon finished reading the note, she stood there stunned. Looking at those words 'Ehehe!', a prominent vein popped on her smooth, white forehead, and her face turned bright red.
Especially since she was still holding the hot porridge, it made her look ridiculously foolish. How could that lazy Captain ever do anything productive? She had been too naive.
Makiya had no intention of involving Soi Fon in things like going to Hueco Mundo or Kisuke's Hogyoku. For some things, keeping her in the dark was truly for her own good.
"He must be out fooling around with some other Captain again!" Soi Fon grumbled resentfully under her breath. "Always disappearing, no one knows where he goes. I hope he drops dead on the road!"
"Achoo!" Inside the Senkaimon, Makiya suddenly sneezed, giving Kisuke Urahara a start.
"What happened? Can a powerhouse of your level actually catch a cold?" Kisuke looked at him with suspicion.
Makiya rubbed his nose and looked around. "It's not a cold. I just feel like someone is talking about me. It wouldn't be that guy Aizen, would it?"
"How could it be?" Kisuke shook his head. "You, although you're a tiny bit less handsome than me, I have to admit that in terms of sheer looks, you're definitely in the top three of the Gotei 13. It's probably some girl thinking about you."
With that, Kisuke wore an expression of confidence and pride. "Besides, if we're talking about Aizen, the one he'd be thinking about first is definitely me. I know he covets the Hogyoku in my possession, but he hasn't had a chance to strike. He's probably obsessing over me in his heart every day."
Makiya felt he had a point, so he scanned their surroundings and chuckled. "If Aizen is looking for an opportunity, isn't this the perfect time? He could kill you here, take the Hogyoku, and dump your body out of the Soul Society. No one would ever find out."
After saying it, Makiya paused. If he were Aizen, now would indeed be the perfect time to plot for the Hogyoku.
"..." Kisuke fell silent.
He rubbed his chin, feeling that Makiya's words made a lot of sense. If he were Aizen, he would definitely find a way to keep a secret eye on himself. Now was indeed a prime opportunity.
"Don't jinx us. My Senkaimon was built in an underground space. How could Aizen know?" Kisuke waved his hand dismissively.
The two continued forward. Spatial turbulence buffeted them constantly. Makiya and Kisuke took turns leading the way, releasing Reiatsu to stabilize the path, which formed a straight, narrow gray trail in the void.
Suddenly, a speck of bright light appeared in the distance. Makiya and Kisuke's expressions turned solemn. They knew that golden light belonged to a creature unique to the Dangai: the Kototsu.
The Kototsu appeared once a day. It did not rely on Reiatsu to survive and followed a fixed patrol route, destroying everything in its path.
Kisuke had calculated the timing when he opened the Senkaimon. Today was not a day for the Kototsu's patrol. Their appearance was extremely strange.
The situation continued to worsen as more golden spots appeared. As time passed, a large number of Kototsu materialized around Makiya and Kisuke, charging toward them.
They had clearly deviated from their patrol tracks. A great hand was manipulating the scene from behind the curtain.
Although there was no evidence, Makiya suspected Aizen. He had clearly released Chisato to purge the Reiatsu of Kyoka Suigetsu from Kisuke and the others who knew the truth, yet he still didn't know how Aizen had managed to predict their actions today.
"...Burst into flames, Chisato!"
"Scream, Benihime!"
The two released their Zanpakuto. To a normal Soul Reaper, the Kototsu was an invincible force, but these two were clearly not ordinary. Even Kisuke's strength was exceptional among the Captains.
Sword light flashed and crimson flames roared. Both used their various techniques to carve a bloody path through the Kototsu assault.
Makiya's performance was more composed, but the violent spatial turbulence left Kisuke overwhelmed. Even with Makiya's help, Kisuke was starting to struggle to maintain his footing and Reiatsu, and the two were gradually drifting apart.
Makiya sheathed his blade at his side, then suddenly drew it. His massive Reiatsu was condensed to the limit and released through the blade, transforming into a brilliant sword light that expanded outward.
A DNF Blade Master skill: Draw Slash.
The sharp strike instantly annihilated a large number of Kototsu, creating a brief vacuum in front of them. But looking out, the previously empty, dark space was now filled with golden spheres. Each sphere was a massive Kototsu.
The golden dots were as dense as stars. They were the scavengers of the Soul Reaper world, acting like the world's immune system—impossible to kill off entirely and partially immune to the attacks of Soul Reapers.
Makiya was doing alright, but Kisuke was reaching his limit. Even with Makiya protecting him, he found it difficult to hold his ground.
In recent years, Kisuke had poured all his focus into the Hogyoku. He had neglected his training in swordsmanship, unarmed combat, movement, and Kido. Even his best sparring partner, Yoruichi, had been taken away by Makiya, causing his combat prowess to drop and his techniques to become rusty.
Makiya wasn't sure when Kisuke would finish developing his Bankai, but it certainly wasn't now.
"There's no other way. I'll send you out first!" Makiya shouted at Kisuke. Chisato suddenly erupted with light as a Blade Master awakening skill made its debut in the Soul Reaper world.
The invisible blade sliced through space, causing a multitude of Kototsu to dissipate into specks of light. Within the shattered space, a vast, desolate gray land could be seen.
Hueco Mundo!
Although they hadn't reached their intended destination, any part of Hueco Mundo would do. With their strength, they could easily dominate the landscape there.
Makiya pulled Kisuke into the spatial rift. A flurry of lights and shadows flashed before his eyes. When the spatial tremors slowly faded, the rift behind them healed itself.
Makiya looked up and found that they had arrived at a rare sight in Hueco Mundo—a building. A throne made of white stone stood high above, and the surrounding atmosphere was heavy and solemn.
"Oh, it seems we have guests visiting today."
An aged voice echoed from atop the throne. A skeleton wearing a crown and a black cloak sat there, propping up its chin with a skeletal hand.
Even though there was nothing inside the dark skull, Makiya could inexplicably feel the other's disdainful emotions.
He was the King of Hueco Mundo, or rather, the former King: Baraggan Louisenbairn!
Makiya helplessly set Kisuke Urahara down and let out a long sigh. "Well, this is great. Where exactly have I ended up..."
Chisato vibrated incessantly; she was very interested in Baraggan's 'Senescence.'