"First like this, then like that, and finally like that."
Inside the newly renovated dojo, Naraku Sora described the specific details of trigger-type Kidō with a serious expression, demonstrating the technique once more.
To an average person, this sounded like some sort of incomprehensible coded language, yet it caused a look of thoughtful contemplation to appear on Aizen's face.
As a Soul Reaper with more than a fair share of talent in the way of Kidō, Aizen had mastered high-level spells long ago, including powerful Hadō ranked above number ninety. Furthermore, he was highly proficient in the various Kidō techniques taught at the Shin'ō Academy, such as double incantation, incantation abandonment, and post-incantation.
Trigger-type Kidō, however, clearly fell outside the academy's curriculum, primarily due to the difficulty of learning it. Simply understanding the construction of the ritual diagrams was no less difficult than learning a new high-level Kidō from scratch. Mastering it to the point of proficiency was harder still.
Fortunately, Naraku Sora had a way of explaining things in a plain and easy-to-understand manner, often pointing directly to the core of the corresponding technique. Learning it wasn't as troublesome as one might imagine.
Of course, that was only from Aizen's perspective. People of different skill levels would perceive the same lesson very differently.
"Hadō Number 4: Byakurai."
Aizen raised his right hand. Reishi gathered spontaneously in his palm, and through nearly perfect control, a relatively simple mark gradually manifested. Along with an infusion of Reiatsu, a sudden crackle of thunder echoed through the dojo. Brilliant lightning erupted, instantly blasting the target ahead into scorched fragments.
When alone with Naraku Sora, Aizen did not intentionally hide his strength. After their previous experiences of life and death together, he didn't have many secrets left in front of this boy. Setting aside their friendship, it seemed he had long since stood on the same side as this fellow.
"The destructive power is somewhat diminished, but not by a significant margin," Aizen said calmly. "However, the preparation time required is too long, making it unsuitable for use in actual combat."
Naraku Sora waved his hand dismissively. "Sōsuke, your thinking is still too conservative. Why would you construct a trigger Kidō right in front of the enemy's face? Can't you learn to be a bit more... 'fair and square'?"
"Besides your hands, don't you have feet?" Naraku continued. "Releasing two Kidō simultaneously should be basic for you, right?"
Aizen looked at him, puzzled. "?"
Seeing his confusion, Naraku Sora felt compelled to demonstrate personally. He pushed himself up and stood straight. "You'll understand if we have a little contest between 'mages.' Don't use anything except Kidō and Flash Step. You'll experience the true utility of trigger Kidō firsthand."
Aizen nodded readily.
Though Naraku Sora was still slightly behind him in terms of raw power, there was no one stronger among their peers from the academy. Moreover, his rate of improvement was even faster than Aizen's own. He had been at the 12th-grade Spiritual Power level at graduation, yet in the blink of an eye, he had almost caught up.
In particular, upon learning that Naraku Sora had successfully broken through to the 4th-grade level, even a genius like Aizen felt a strange sense of urgency. The exaggerated speed of his growth had once made Aizen suspect that Naraku Sora was taking some kind of forbidden drug developed by Shutara Senjumaru.
"Self-destruction, the black dog of Rondanini! Look upon it with dread, then burn and claw at your own throat! Bakudō Number 9: Geki!"
As Naraku traced his fingers through the air, red lines manifested, instantly transforming into a beam of light that descended toward Aizen.
"...Trace, burn out, and spill by your own hand. Hadō Number 14: Zantetsu!"
Immediately following was a Kidō strike that resembled a sword pressure. The crescent-shaped blast tore through the dojo, making a sound like ripping silk. Fissures appeared on the ground as the sharp intent rushed forward.
As Aizen sidestepped to dodge, a shield formed via incantation abandonment appeared out of thin air, firmly blocking the flying strike with the ring of clashing metal.
"Hadō Number 31: Shakkahō."
He didn't particularly like this spell because it was too flashy and easily attracted attention. At the moment, however, it was the most appropriate choice. It wouldn't cause too much damage to the dojo while still allowing him to control the rhythm of the duel. Aizen was curious to see how Naraku Sora would utilize trigger Kidō in battle.
"...Truth and temperance, the wall of sinless dreams, stand only upon it! Hadō Number 33: Sōkatsui!"
One Kidō incantation after another was recited. The surging Reiatsu of the spells intertwined, weaving an invisible net that blanketed Aizen. Gorgeous light bloomed to the limit as explosive sounds rang out. Intense flames mixed with jumping bolts of electricity, attacking everything within range indiscriminately.
Kidō released head-on like this would struggle to hit Aizen. Since direct hits weren't working, Naraku simply expanded the area of attack. By utilizing the limitations of the dojo, he forced his opponent to take the damage.
Aizen's expression remained unchanged throughout. His Flash Step allowed him to shift and dodge the cascading Kidō impacts with ease. Even when he encountered a spell he couldn't dodge, he simply released a defensive Bakudō or another Hadō to neutralize it—a technique similar to "Anti-Kidō Combat."
What surprised Aizen, however, was that Naraku Sora's proficiency in Kidō seemed not a bit weaker than his own. Some spells even performed slightly better. For example, the most frequently used Shakkahō. Even when using incantation abandonment, Naraku's Shakkahō suffered no loss in power; in fact, it was stronger than a full incantation from others.
This only happened when someone had perfectly mastered a specific Kidō. If it were just one or two spells, Aizen wouldn't be so shocked, but every Kidō Naraku had released since the start of the fight met this standard.
It was quite unexpected.
Yet, just as Aizen was marveling at this, he suddenly realized the floor beneath his feet felt slightly off. In the instant he instinctively looked down—
Blinding fire shot toward the ceiling. In a flash, a violent roar of thunder followed, and the scorching light swallowed the unprepared Aizen whole. A condensation of brilliance and splendor bloomed magnificently at that moment.
At the critical second, Aizen used a silent Dankū. A sturdy, invisible barrier appeared out of nowhere, steadily and easily blocking the majority of the roaring flames. The stray shocks that leaked through were effortlessly snuffed out by his overwhelming Reiatsu.
When everything settled, Aizen frowned as he looked at the spot where the Kidō had erupted. A few traces of Kidō Reiatsu remained on the scorched floor. Judging by the marks, it was indeed a trigger-type Kidō that had just been constructed.
Aizen flashed back through the fragments of the battle in his mind. He replayed Naraku Sora's movements frame by frame until he finally caught an anomaly in the Reiatsu beneath the boy's feet during one specific Flash Step.
"Sōsuke, is Kidō really such an inconvenient thing?"
Naraku Sora grinned from the side, looking quite proud of himself. "Besides using my feet, I could even release Kidō from my head—it just wouldn't look very good."
"But we Soul Reapers have never been ones to sweat the small stuff. Come, come, let's learn it from the beginning."
Aizen was silent for a moment. "..."
He was now hesitating on whether he should continue learning this or not.