Soi Fon's words reminded Kurotsuki Renya of his Zanpakutō's Shikai, whose name was Tenraiban. When released, the blade itself vanished, dark clouds forming above, and from them descended a thunderbolt—the very embodiment of Tenraiban.
Tenraiban manifested as a short spear, just over four shaku in length. Of course, with Renya's current height of barely 1.4 meters, it hardly felt short at all.
It possessed two core abilities. The first: from the darkened skies, Tenraiban could call down thunderbolts to strike enemies. The destructive power was immense. Against Captains, resistance was possible, but even beings with monstrous physical durability—like Zaraki Kenpachi—could not endure without sustaining wounds and losing mobility.
The second ability: Tenraiban could directly convert Renya's reiryoku into pure lightning-element energy. The efficiency of this conversion was remarkable—surpassing even the chanting forms of Hadō #63 Raikōhō and Hadō #88 Hiryū Gekizoku Shinten Raihō. This was precisely why Renya could cast such spells at all.
Even so, his reserves were limited. At best, his reiryoku could support three full-powered blasts of the #88 spell. Beyond that, sustaining the technique was impossible.
The destructive power of Hiryū Gekizoku Shinten Raihō was enormous—one of the highest-level Hadō. Its force eclipsed Raikōhō, and stood just beneath the dreaded Hadō #90 Kurohitsugi. One only needed to recall how Kurohitsugi, even cast without full incantation, could nearly annihilate Komamura Sajin to understand. If Renya's #88 spell could push even a third of that might, its potential was fearsome.
Even Zaraki Kenpachi, with his titanic physique, would struggle to withstand more than two direct blasts. But during their battle, Renya's reiryoku had already been depleted, leaving him unable to unleash a second round.
Moreover, the Raijin Wings he manifested during combat were also born of Tenraiban's second ability. When his thunder cannon failed, Renya poured his last scraps of reiryoku into an explosive transference, attempting to mimic true Shunkō. Instead, the purer lightning energy gave form to Raijin no Tsubasa, thunder wings that boosted his speed to levels rivaling perfected Shunkō—and perhaps with room to grow beyond.
With Raijin Wings, Renya no longer needed to pursue Raijin Shunkō specifically. Instead, he could focus on blending his lightning with other attributes, like Fire or Wind, amplifying both destructive power and sustainability.
Of course, instantaneous techniques devoured vast amounts of reiryoku. His current level couldn't maintain them for long. Only by raising his spiritual pressure to the Seventh Rank could he wield them freely.
The thunder cannon and Raijin Wings were merely the beginning of Tenraiban's potential. Renya was certain more techniques lay dormant.
Shaping lightning into beasts or weapons—Raijū Keitai (Thunder Shaping).
Accelerating metal projectiles with magnetism—Railgun.
Wreathing his fists in thunder to strike in close quarters—Raijin Ken.
Using the heat of lightning to melt and forge metal—Raijin no Kōzai (Thunder Metallurgy).
Channeling bolts into precise strikes at pressure points—Raijin Keiketsu (Thunder Acupuncture).
He even joked inwardly: or perhaps even curing bad habits with shock therapy…
His mind brimmed with possibilities. Once healed, he could test them one by one.
Renya explained Tenraiban's two core abilities to Soi Fon. To her, he had no reason to conceal them. He already knew all of her Zanpakutō's secrets, and she was not only his Captain but also his mentor. Perhaps even… more, someday.
Soi Fon listened intently before speaking. "A formidable Zanpakutō. Especially the second ability—it carries limitless potential."
Renya nodded. "I already have some ideas. The specifics… will take trial and error."
Soi Fon regarded him carefully. "You've manifested Shikai and shown you can contend with Captains. Remaining as my adjutant is no longer suitable."
Renya smiled faintly. "So, am I being promoted?"
She gave a soft hum. "Not to Vice-Captain of the Patrol Corps. I intend for you to lead the Third Unit—Worm's Nest Surveillance."
"The Third Unit? The one overseeing the Nest of Maggots?" Renya was surprised.
The Worm's Nest imprisoned those deemed threats to the Seireitei—not for raw strength, but for dangerous thoughts, behavior, or interference with official duties. Once judged, they were investigated, arrested, and confined. Many of these souls vanished under the pretense of leaving the Gotei 13—but in truth, no such resignation existed. Those who withdrew were forcibly confined, their Zanpakutō confiscated.
Within the Nest, no inmate retained weapons. Thus, its warden had to be capable of subduing every prisoner barehanded.
Decades ago, the role had been held by Kisuke Urahara, who later ascended to Captain of the 12th Division, founded the Shinigami Research and Development Institute, and even recruited Mayuri Kurotsuchi—then imprisoned in the Nest—as his deputy. After Urahara's departure, Soi Fon herself had once overseen it, until taking full command of the Stealth Force following Yoruichi Shihōin's exit.
Now, she judged Renya strong enough to shoulder the role. Even without his Zanpakutō, with his Raijin techniques, his combat strength rivaled top Vice-Captains.
It was a dangerous position, but Renya welcomed it. The Nest's underground location meant concealment, and after his clash with Zaraki had drawn so much attention, obscurity was exactly what he needed.
Moreover, leading the Surveillance Unit meant broader intelligence oversight than even the Patrol Corps.
"I accept," Renya said firmly. "I'll serve in the Surveillance Team."
"Good. Begin after your recovery."
Soi Fon rose to leave.
Renya's heart sank slightly. "…Is Captain already leaving?"
An unfamiliar ache stirred within him. Somewhere along the way, he had grown attached to her—this stern, unyielding woman who had pushed him, trained him, guarded him.
He had seen her strict side, her serious side, and—at rare times—her softer, almost awkward side. Especially now, after helping him awaken his Shikai and staying at his side for a day and a half, he felt it clearly.
Soi Fon studied him for a moment, then softened her tone. "I've been here long enough. My duties still demand me. But I'll return tonight."
Renya smiled faintly. "Then… see you later, Captain."
"…Mn."
She turned and left the room. Only once she had walked a long distance did she allow herself a quiet sigh.
That look in your eyes… I know it well. It was once my own.