That was a lie.
Rian hadn't told the truth. In reality, there was an item that could allow a character from another reality to become a Herald's servant: the Contract Letter.
A Servant Herald possessed the same rights as any other Herald, with one condition: their life was bound to the master Herald, and they could not betray them.
If the master died, the servant would die as well. However, if the servant died, the master would remain alive.
Even so, if a Servant were to die… Riab could potentially revive them using a certain item.
Still, Rian tried as much as possible not to involve Koneko with the Infinity Room, which he considered dangerous.
On the other hand, Koneko continued gazing at the nighttime view of Kuoh Town, her golden-yellow eyes trembling faintly.
Slowly, she closed her eyes, letting sorrow and regret flow through her.
The atmosphere around them was silent, as if even time held its breath. In her heart, Koneko found the courage to speak.
With a decisive motion, Koneko opened her eyes. Her gaze, full of determination, lit up her face as she reached for Rian's collar and, swiftly yet gently, pressed her lips against his.
Instantly, the silence of the night felt warm. Koneko's heart pounded fiercely, her cheeks flushed, yet her lips remained pressed against his.
Rian stayed still, allowing Koneko to kiss him.
With Six Eyes, Rian could easily have resisted or dodged the kiss, but this time, he simply wanted to comfort his "beloved cat."
He chose to let Koneko dictate the duration, however long she wished.
Five minutes later, their lips finally parted. Rian smiled softly, looking at Koneko, whose face was flushed all the way up to her Nekomata ears.
"…D-don't take too long," Koneko muttered, trying to calm herself while turning her face away. "Hurry back…"
Rian squinted, then gently cupped Koneko's chin with his right hand and kissed her again.
Koneko remained silent, her face still flushed. Her eyes were tightly shut, as if allowing the moment to flow uninterrupted.
In the next instant, Rian's body vanished from the DxD world like sand blown away by the wind, disappearing mid-kiss and leaving Koneko alone there.
***
[Infinity Room]
Inside the vast training hall, Rian stood atop a white marble-floored combat stage, surrounded by towering white pillars that encircled the arena.
The stage itself seemed to float in the middle of an endless desert.
Ten steps ahead of Rian, a man stood—pink hair slightly combed forward, tattoos etched across his body, and an extra pair of eyes beneath his normal ones.
He wore a bright white kimono with black trim, a black scarf wrapped around his neck, and black sandals.
It was none other than Ryomen Sukuna—or more precisely, Sukuna in Yuji's form.
Rian and Sukuna locked eyes in silence, both standing tall and still, seemingly waiting for the first move from the other.
Meanwhile, outside the combat arena, Fear sat calmly on a bench with Alice leaning against his lap.
They had been watching the training session unfold from the very beginning, precisely from some time ago.
At the moment, Rian had rented the training house for two days. This was where he had been spending his time over the past several days.
Before facing Sukuna, Rian first sparred with Naobito Zen'in to study the Secret Art: Falling Blossom Emotion.
He also practiced Simple Domain: New Shadow Style through sparring with Atsuya Kusakabe.
In addition, Rian learned the Breathing Styles from the world of Kimetsu no Yaiba: Thunder Breathing Style, which he planned to apply as a laijutsu technique to execute the New Shadow Style slashes.
With the addition of Jet Kun Do and Tai Chi, Rian ultimately mastered four different martial arts styles simultaneously, making him an extremely versatile and formidable fighter.
With the help of his Six Eyes, Rian was able to quickly understand the fundamentals of all these techniques and put them into practice.
Now, it was only a matter of time before all the Jujutsu techniques and martial arts skills he had learned could be utilized outside the Infinity Room.
However, all of that could wait for now, because Rian's focus was… to study and fully understand Domain Expansion through his battle with Sukuna.
In an instant, Rian activated Maximum Output: Reverse Cursed Technique, enveloping his mind and heightening his concentration to the peak.
Then, he raised his right hand, his fingers forming a distinctive position.
Rian's index finger was straight, his middle finger pressed against it, while the other fingers curled neatly.
The gesture was simple, yet charged with intense focus.
At the same time, Sukuna raised both of his palms, facing forward.
His index fingers bent toward the thumbs, the middle fingers pressed firmly against the index, while the ring and pinky fingers curled into the palms, thumbs standing upright.
His left hand mirrored the right, slightly wider apart, creating a perfect symmetrical ritual.
"Domain," Rian said seriously.
"…Expansion," Sukuna replied in a cold tone.
Instantly, Sukuna and Rian smiled and simultaneously shouted the names of their Domains:
"Malevolent Shrine!"
{Fukuma Mizushi}
"Infinity Void."
{Muryo Kusho}
The air around the arena instantly thickened and vibrated, signaling that the laws of reality were beginning to bend under the influence of each Domain, preparing for a battle that surpassed normal limits.
From the floor beneath Sukuna's feet, his shadow cracked and flowed like thick black liquid. Skulls emerged, piling atop one another.
Gradually, a colossal shrine with open mouths on all four sides took shape.
Malevolent Shrine had manifested.
Meanwhile, Rian's Infinity Void barrier expanded rapidly, engulfing Sukuna along with the demonic shrine, forming a black sphere with a ten-meter radius.
Immediately, Infinity Void and Malevolent Shrine collided, creating a gravitational clash so immense that it tore at the space around them.
As a result of the impact, the ground around the black sphere was heavily compressed, forming a massive crater while a rumbling roar shook the air.
However, the clash between the two Domains lasted only five seconds—before Infinity Void cracked and shattered into pieces.
This revealed Sukuna standing tall, Malevolent Shrine looming majestically behind him.
"Damn," Rian cursed.
Sukuna grinned, and in the next instant, thousands of Dismantle and Cleave slashes rained down on Rian from every direction.
Dismantle was a basic slash that could be used on both close and distant targets, effective against inanimate objects, cursed spirits, or sorcerers.
Meanwhile, Cleave was a stronger slash, adjusting to the target's durability to deliver a fatal blow, often cutting the target into multiple pieces.
The slashes struck Rian, and it happened in an instant. Within five seconds, Rian's body was reduced to a heap of shredded flesh, blood splattering everywhere.
The next moment, the desert arena transformed into an all-white room; Sukuna vanished, and Rian's body was fully restored.
Rian stood in the center of the room, exhaling heavily, then turned toward Fear, who was sitting not far away.
Fear remained calm, even after witnessing the massacre—Rian had just taken thousands of Dismantle and Cleave slashes, reducing his body to a heap of shredded flesh.
Normally, Fear would have been triggered, acting like a psychopathic torturer due to her curse. But this time, she didn't.
For good reason. Fear realized that everything that had happened in the training house was merely a simulation, albeit one that felt incredibly real.
"Are you okay?" Fear asked, her tone curious. "You've been training for ten hours straight. Aren't you tired?"
Rian smiled warmly. "I'm fine. It's just… you look really beautiful sitting there so quietly."
Fear's face immediately flushed, her mouth opening, yet she couldn't utter a single word. Seeing this, Alice merely let out a soft sigh.
After that, Rian opened the training house's settings menu, focused his mind, and resumed his intensive training to face Sukuna once again.
From the second to the fourth rounds, although he was still losing in the Domain battle against Sukuna, Rian managed to endure 30 seconds of attacks from the Malevolent Shrine.
Instead of relying solely on his mind, Rian began channeling Maximum Reverse Cursed Technique throughout his entire body with greater precision than before.
From the fourth to the seventh rounds, his endurance increased rapidly.
With Reverse Cursed Technique continuously active, Rian was able to withstand attacks for longer periods, even managing to exchange blows while both Domains were active.
Learning from previous failures, he then modified Infinity Void using a Binding Vow as an experiment.
The result: by the eighth round, the battle ended in a draw.
From the ninth to the fifteenth rounds, Rian continued to perfect the Infinity Void formula. He added extra Binding Vows, new hand seals, and specialized incantations.
With these improvements, Rian finally managed to win the Domain battle against Sukuna.
However, just as he was about to take it further—perfecting his Domain by emulating the Malevolent Shrine's ability to activate without a barrier—the rental time for the training house ran out.
Instead of extending the duration, Rian decided to leave immediately to attend to other matters waiting for him.
At the very least, in a single full day, Rian had learned and mastered a great deal.