"Sit upon the frozen heavens, Hyorinmaru!"
"Illuminate the Ten Thousand Realms—Hikari"
The environment of the underground space underwent a sudden and violent change.
Two Shikai release commands echoed through the space almost simultaneously as spiritual pressure erupted. In an instant, the world was severed in two.
A frigid chill exploded around Toshiro. Moisture in the air condensed into ice, forming a dragon that coiled around him. A chain tipped with a crescent-shaped blade extended from the hilt of his sword, swaying like a dragon's tail. As Hyorinmaru was released, the temperature of the surrounding air plummeted, and frost rapidly spread across the ground with Toshiro as its center.
Opposite him, the Hikari in Suō Tsukasa's hand radiated a starkly different brilliance. Soft, pure light poured out from around his body; wherever the light touched, Toshiro's frozen domain was quietly partitioned. The boundary between light and ice was sharp and distinct, where two different worlds met.
With the confidence provided by Suō Tsukasa's Kaido healing abilities, the two had recently begun incorporating their Zanpakuto releases into all their practical combat drills.
"Tsukasa, watch out!"
"Ryusenka!"
Toshiro's eyes sharpened as his body moved in a blur. Hyorinmaru swept horizontally, freezing everything in the blade's path. Following the direction pointed by the tip, ice blades extended further from the frozen areas to strike.
Facing this rapid, large-scale freezing slash, Suō Tsukasa's expression remained calm as he swung his sword to meet it. A dazzling burst of light flashed, completely dissolving the ice blades. He concentrated the light into a single point, dispersing the low temperature and inhibiting the formation of ice crystals, thereby neutralizing the attack.
Ice crystals turned to water, and mist began to rise.
The residual power of the Ryusenka still vibrated in the air, and fine ice crystals continued to creep toward Suō Tsukasa. Between combatants of equal level, Hyorinmaru's innate ability to control the weather granted it a significant advantage.
Feeling the plummeting temperature around him and a slight sluggishness in his movements, the light on Suō Tsukasa's body began to circulate more intensely. Standing on the borderline of light and ice, the crescent chain-tail from the hilt of Hyorinmaru suddenly shot out from the mist, attempting to bind the Hikari in Suō Tsukasa's hand.
"Hado No. 4: Byakurai."
Suō Tsukasa looked at the crescent blade flying through the air. He raised his left hand slightly, and a bolt of white lightning shot from his fingertips, knocking away the approaching chain.
The lightning brushed past Toshiro. He kept his body low, charging forward with his blade. He was entirely unaffected by the Byakurai; his speed was incredible, leaving a trail of frost behind him. Hyorinmaru thrust upward from below, its cold tip aiming for Suō Tsukasa's neck and shoulder.
Suō Tsukasa's reaction was lightning-fast. The moment Toshiro appeared from behind the mist, Tsukasa had deduced his tactical intent. Pivoting on his toe, he swung his blade diagonally to the right.
"Oh?"
"A new move."
There was no expected spray of blood. Feeling the sensation transmitted through the blade, Suō Tsukasa raised an eyebrow. The figure of Toshiro in front of him shattered, turning into fine ice crystals, while a thin layer of ice spread from the tip of the blade to Suō Tsukasa's right arm.
At that exact moment:
"Guncho Tsurara!"
Swish, swish, swish—sharp ice projectiles emitting freezing air shot toward Suō Tsukasa like a torrential downpour.
"Good thinking."
Suō Tsukasa chuckled, shattering the thin ice on his body as the fragments hit the floor. His blade danced, completely pulverizing the oncoming barrage.
A few seconds later:
"Hyoro!"
Toshiro reappeared, pointing his blade directly at Suō Tsukasa's feet. Pillars of ice surged upward, and the released freezing air began to corrode his spiritual nerves and muscles.
"The formation speed of the Hyoro is ten percent faster than yesterday," Suō Tsukasa praised inwardly, yet no panic showed on his face. He gathered a portion of his light onto his legs, engaging in a back-and-forth struggle with the frost.
A sharp streak of light shot directly at Suō Tsukasa's chest. It pierced through his figure, but only stirred a ripple of light and shadow.
Toshiro's pupils constricted as alarm bells rang in his mind. The moment the thrust missed, he knew something was wrong. He twisted his body, attempting to retreat.
But it was too late.
The tip of Hikari flashed before his eyes. His vision turned white; Toshiro's sight had been temporarily stripped away by Suō Tsukasa. Relying on the training they had done over this period, he managed to hold out for several rounds through sheer effort.
"Let's stop here for today."
As the blade came to rest on Toshiro's shoulder, Suō Tsukasa's voice sounded in his ear. The previous adaptation training had long since concluded, and their recent practical drills were basic exercises in restraint.
Toshiro stood still with his eyes closed. The sensation of his vision being stripped away had not yet fully receded. Having to rely solely on his other senses and muscle memory to endure those few exchanges after losing his sight had been brief, yet far more mentally taxing than before.
"Since when could your Hikari strip away vision?"
Exhaling a long breath of turbid air, Toshiro opened his eyes to see Suō Tsukasa sheathing his sword. The frost on Hyorinmaru silently withdrew, and the frost on the ground melted into puddles.
"To be more accurate, it's just a glare—similar to looking directly at the noon sun, but more concentrated and sudden. Within a very short time, I cover your eyes with high-frequency intense light, causing short-term blindness. The duration depends on the opponent's physical constitution; for you, it's only an effective interference for about ten seconds."
"In actual combat, that's more than enough time," Toshiro remarked, blinking away the lingering circular spots in his eyes.
Suō Tsukasa paused, his tone becoming more serious.
"Usually, our battles rely on the five senses for judgment. We lack targeted training. Just like today, how you used an ice clone as the trigger for a control chain—that was specifically exploiting my vision. I have an idea: conducting combat practice while some senses are sealed. What do you think? Once we get used to this kind of interference, we'll be much more composed when facing similar abilities or emergencies in the future."
"Mhm. How specifically?" Toshiro nodded and asked.
Suō Tsukasa had long since mapped this out and answered fluently.
"One step at a time. We start with vision; it's what we rely on most and is the easiest place for a flaw to emerge. Once we overcome that, the sensitivity and coordination of our other senses will be forced to improve. After building a solid foundation, we can gradually seal the other five senses until we primarily fight using spiritual perception."
"What we need to train is not replacing the five senses with spiritual perception, but tempering it into a deeper instinct. When the information from spiritual perception differs from what the other senses report, even a split second of hesitation or the need to confirm can be critical."
Spiritual perception could detect an enemy's location from a distance, but its effect in the heat of battle was less obvious. When spiritual pressures clashed at close range, the auras became mixed, making it extremely difficult to gain useful information through perception alone.
Suō Tsukasa didn't know exactly what it felt like to be under the influence of Kyoka Suigetsu, but he knew that spiritual perception was the only possible way to detect the abnormality of Aizen's illusions. In the original story, Unohana Retsu managed to discover the abnormality of Aizen's "corpse" through spiritual perception even when her five senses were deceived.
Suō Tsukasa did not want a day to come where his blade pierced the body of a friend or loved one. To prevent that, targeted training was essential.
"When do we start?" Toshiro made his decision and nodded curtly.
"No rush. Let's prepare mentally first and start in a few days. Don't let the fact that I proposed this plan fool you; I'm not actually sure how effective it will be. It's possible we'll work hard for a long time and gain nothing, wasting our time entirely," Suō Tsukasa admitted with a touch of helplessness.
"It doesn't matter. I'll be with you," Toshiro said. His trust in Suō Tsukasa was absolute, his expression calm and steadfast.
"Thank you."
Suō Tsukasa suddenly felt that, in the face of such a gaze, his worries were somewhat redundant.