The "Dualities" refer to the Yin and Yang depicted in the Taiji diagram.
Her name is taken from the "shiki" (formula/ceremony) of mathematical formulas and the "shiki" of Shikigami.
In other words, it is proof of being a Universal Wish-Granting Machine.
To one who possesses this skill, ordinary parameters and numerical values are meaningless.
By engaging in the union of Yin and Yang with Shiki Ryougi, the Host has acquired this very skill!
The effect of this skill is to cause an invisible anomaly in the Host's physical fitness; the Host's combat power can no longer be represented by visible numerical values!
At the moment Haruka Kasugano acquired this skill, he suddenly felt the "key" to his Root become exceptionally powerful.
Ah...
His "Holy Sword" suddenly grew significantly larger and longer, and its hardness and durability clearly became even more terrifying.
Huh?
He didn't notice any changes in the rest of his body. Could it be that the so-called "indescribable physical fitness" purely referred to becoming stronger in this specific area?
Tsk...
It was already difficult enough to enter and exit the Swirl of the Root; now that he had become even stronger, wouldn't it be even harder? No, look at it another way: he had become much more durable. Doesn't that mean he's no longer a "quick-shot" in front of Shiki?
Quack quack quack!
[Reward: One-time use Noble Phantasm "Laus St. Claudii (Ode to the Imperial Virgin) B"! ]
Wait, isn't this Nero's Noble Phantasm? They even threw this in, though it's only a single-use item. Tsk... this reward for 50% Infidelity Progress is a bit stingy. Whatever. The biggest gain is Shiki herself!
Jie jie jie jie~!
---------
Around 10:00 PM.
Haruka Kasugano asked Azaka Kokutou out again. Because Shiki's "Root" was so tight, Haruka Kasugano felt a bit drained, but he couldn't skip the fourth day's date. He had to continue Azaka's "education" every day. Otherwise, how would she ever become "his shape"?
"Mmph... mmph... slurp..."
As soon as Azaka walked into the hotel room Haruka Kasugano had booked, he pulled her onto the bed. Her eyes were still vacant, and she did whatever Haruka Kasugano told her to do. Right now, she was helping Haruka Kasugano "clean his instrument."
"Yo, you're getting more and more skilled. You really have a talent for this!" Haruka Kasugano teased.
Azaka didn't respond, continuing to lick and taste like a lost soul. Aha, trying to resist me by shutting down, are we? Seems I haven't let you feel enough pleasure yet! However, since his stamina hadn't fully recovered yet, he decided: I'll deal with you tomorrow morning!
"Don't go back tonight. Stay over," Haruka Kasugano said, stroking Azaka's fair skin.
"Mmh..." Azaka didn't object, still looking lifeless. Haruka Kasugano wasn't in a hurry; he had already planned out the "torture" for tomorrow morning.
"Wonderful. Now it's my turn to help you clean up, isn't it?" Haruka Kasugano smiled.
"Eh?" A different expression finally flickered across Azaka's face. She never expected Haruka Kasugano to make such a request. To be honest, her first time was taken by him; he was her "enlightenment teacher." There were still many things she didn't know. For instance, what Haruka Kasugano just suggested—"cleaning her up." This was completely outside her expectations.
She subconsciously believed that men only wanted women to serve them and make them happy. Do they actually get happy serving women too?
While she was dazed, Haruka Kasugano had already picked her up and flipped her around, placing her beautiful legs and her "scented pomelo" right before his eyes. Looking at that exquisite crimson bud, Haruka Kasugano couldn't help but lick his lips.
Azaka watched him, completely failing to understand. Is he going to help me... but why? Would he find that fun?
"Ah~~~! Ah..."
Suddenly, she couldn't help but feel a surge of joy.
Ah! Ah!
How can this be... how can there be this kind of feeling... this is too...
This wasn't the first time Haruka Kasugano had "cleaned" her like this, but back then, under the influence of the drug, her consciousness was hazy. This was her first time, fully sober, having Haruka Kasugano kiss that crimson bud. It wasn't that she disliked normal union with him, but rather that it was so "rough" that she felt resistant.
So gentle... so soft... this feeling—Kimochi!!!
Azaka couldn't hold out. Her emotions reached their peak. Her waist arched like a leaping carp. Like a spider, her four limbs braced against the sheets, forming a bridge.
Splurge—
A spray instantly splashed onto Haruka Kasugano's face. But Haruka Kasugano didn't plan on letting her go; he continued to kiss the crimson until dawn.
"No... this feeling... this gentle pleasure... I'm going to become strange... Ahhhhh—!"
[Ding~! Azaka Kokutou has sunk into the depths. Infidelity Progress +10%!]
[Stacked for the Host.]
Seeing Azaka's blushing and excited face, the corners of Haruka Kasugano's mouth curled into an indescribable angle. Trying to play with me? You're still too green!
After several hours of continuous offensive, Azaka was "broken" once again. She lay on the bed with hollow eyes, her body numb. Before this, she had reached the peak over twenty times. Her body's defense mechanisms had kicked in, leaving her entirely paralyzed.
Seeing this, Haruka Kasugano finally let her be. He pulled the fragrant "Flower" toward him like a body pillow and fell peacefully asleep.
---------
Around 3:00 AM.
Haruka Kasugano woke up suddenly. He sensed a message from Souren Araya. He walked to the window, opened it, and took a small note from a pigeon.
"Hmm? Alba has arrived in Mifune City? Wants me to come over for a meeting?"
Interesting! Haruka Kasugano got dressed, felt Azaka's fresh, snowy skin one last time, and headed out. He arrived at the Ogawa Apartment complex. Souren Araya was sitting with a flashy-looking man in red.
"Alba, this is the Haruka Kasugano I told you about," Araya introduced.
"Oh? You're Haruka Kasugano? Hello there~!" Alba grinned.
"Hello." Haruka Kasugano walked over and sat down.
"Good that you're here. Let's start the meeting. Let's discuss how to reach the Root," Araya said, looking quite displeased.
------
Cornelius Alba, the man known as the "Red Magus," was an old acquaintance of Touko Aozaki and Souren Araya from the London Mages' Association. He was also the next head of the Sponheim Abbey. He harbored a deep resentment and absolute hatred for Touko Aozaki, who was younger than him but far more talented. To achieve his goals, he spared no effort in helping Souren Araya and had even sworn an oath to kill Touko.
He was once a leader in the Association's hunt for Noritaka Emiya and was one of the culprits who led Kiritsugu Emiya toward his breakdown. Though he had some accomplishments in Rune magic and puppet-making, he was inferior to Touko in both, which stayed as a thorn in his side.
Now, three men with ill intentions sat around a round table, plotting their next moves.
"The experiment at Ogawa Apartment has been a total failure," Souren Araya said, his brow furrowed in annoyance. "Today marks the fourth time an error has occurred. And today's error was especially severe—that puppet actually developed its own will."