Undetectable

While Mazumi Mami was sharing a warm embrace with the three girls in the dormitory, at the other end of the city, the private research institute under the Sakayanagi family was brightly lit and bustling with activity.

In the corridors, researchers in white lab coats hurried past, carrying various test reports and samples as they shuttled between departments.

The low hum of operating instruments mingled with occasional commands, forming the unique background soundtrack of the night.

The cause of it all was the bottle of Milky Nutrient Solution that Sakayanagi Arisu had brought back from school.

At this moment, in the deepest core experimental area of the institute, a massive one-way glass panel separated the observation room from the testing room.

Sakayanagi Narumori stood before the glass, hands clasped behind his back, his gaze fixed on the scene inside the testing room.

Inside, Sakayanagi Arisu had already changed into a white hospital gown, her frail figure appearing even thinner in the loose clothing.

She lay calmly on the MRI scanner's examination bed, and following the operator's instructions, she was slowly fed into the circular tunnel at the center of the machine.

"Professor Sato, have the other test results come out?"

Sakayanagi Narumori asked without turning around.

Standing behind him was an elderly man with graying hair and a gaunt face.

He wore a white lab coat, and the badge on his chest read "Ichiro Sato, Chief Researcher."

He was the most senior and capable lead researcher at the Sakayanagi Research Institute, having been responsible for monitoring Sakayanagi Arisu's health and researching treatment plans since she was a child.

Professor Sato adjusted his reading glasses, opened the tablet in his hands, and spoke with a complex tone: "They have, sir."

He paused, as if weighing his words: "After our comprehensive chemical composition analysis, spectral testing, and bioactivity assays... the conclusion is that this nutrient solution, in terms of its material composition, is indeed a very ordinary nutrient solution. We found no special ingredients or traces of extraordinary technology."

"Oh?"

Sakayanagi Narumori raised an eyebrow and turned around, his gaze sharp with scrutiny. "Are you saying... that Arisu's improvement in health is just her imagination?"

"No."

Professor Sato shook his head without hesitation, his tone firm. "The young lady's physical condition has indeed improved—this can be clearly confirmed by the data."

He displayed several sets of data charts on the tablet for Sakayanagi Narumori to see: "Please look here—these are the blood routine data collected from the young lady today, these are her cardiopulmonary function indicators, and these are the results of her muscle reaction speed tests... Every single piece of data forms a stark contrast with her previous records. While it's not a earth-shattering change, the overall trend toward improvement is very clear."

He looked up, a mix of emotion and shame flickering across his aged face: "The young lady has undergone countless physical examinations in this institute since she was a child. We know the normal fluctuation range of every data point by heart. I dare say no one understands her physical condition better than we do."

"And today's data shows—her physical state has indeed reached its best level in recent years."

Professor Sato set down the tablet, his voice dropping slightly. "We spent so many years, invested so much manpower and resources, and couldn't solve the problem... yet it was improved by a seemingly ordinary bottle of nutrient solution. As so-called 'experts,' we can't help but feel deeply ashamed."

Hearing this, Sakayanagi Narumori was silent for a moment before speaking slowly: "You don't need to feel ashamed. This nutrient solution is something the heir of Mizuki Heavy Industries personally consumes. Given the strength and foundation of the Mizuki family, it's not surprising that they possess technology far beyond common understanding."

"I see..."

Professor Sato nodded thoughtfully. "If it's Mizuki family technology, then it's no wonder. After all, that lord's family has accumulated expertise in biotechnology and materials engineering that we simply cannot match."

However, Sakayanagi Narumori shifted his tone, his gaze turning sharp: "But, Professor Sato—you just said this is just an ordinary nutrient solution. With your experience and research ability, couldn't you find even a single clue?"

Professor Sato gave a bitter smile and shook his head frankly: "I'm sorry, sir. The formula of this nutrient solution is entirely beyond my ability to comprehend. The underlying principles involved are likely beyond what current mainstream technology can explain."

He pondered for a moment before offering his speculation: "I suspect... the special properties of this nutrient solution are only activated after entering the human body. Simple in vitro testing cannot trigger its true mechanism. In other words—without using the human body as a medium, we may never unlock its secrets."

Sakayanagi Narumori was silent for a long time before slowly nodding: "If that's the case... then we can only wait. Wait for Arisu's subsequent physical feedback data to come in, and see if we can find a breakthrough."

Professor Sato bowed: "Understood. I will continue to track the young lady's physical indicators."

Some time later, the door to the testing room opened.

Sakayanagi Arisu had changed back into her school uniform, holding her signature cane as she walked out slowly.

Though her steps were still not steady, there was a clear improvement compared to the past, when every step seemed to drain a great deal of energy.

She walked up to Sakayanagi Narumori and Professor Sato, tilting her head slightly: "So, Father, Grandpa Sato—any results?"

Professor Sato exchanged a glance with Sakayanagi Narumori, then lowered his head apologetically: "I'm very sorry, young lady... although we conducted a comprehensive examination, we still couldn't crack the secret of this nutrient solution."

Sakayanagi Arisu was silent for a moment, but there wasn't much surprise on her face.

She murmured softly: "I had some mental preparation... but hearing it directly still leaves me a little disappointed."

Professor Sato looked at the girl he had cared for since childhood, a trace of pain and guilt flashing in his eyes: "I'm sorry, young lady. It's my lack of ability..."

"It's okay, Grandpa Sato."

Sakayanagi Arisu looked up, offering a faint smile. "You've worked very hard. I remember everything you've done for me all these years."

That heartfelt understanding and gratitude made Professor Sato's eyes redden slightly.

He bowed deeply: "Thank you for your understanding, young lady..."

"Alright, Professor Sato."

Sakayanagi Narumori spoke up at the right moment, his tone carrying a balance of consideration and authority. "You may go rest now. Please step up the follow-up research work. Even if we can't fully replicate the original, if we can produce a close imitation—try again with all your effort."

"As you command, sir. I will do my utmost."

Professor Sato responded solemnly, bowed once more to the father and daughter, then turned and left the room.

The heavy door closed, and in the well-insulated room, only Sakayanagi Narumori and Sakayanagi Arisu remained.

After a brief silence, Sakayanagi Narumori broke it first: "It seems now that the only way to truly solve your health problem is to directly seek help from young master Mazumi."

A meaningful smile crept onto his lips: "But... for you, that might not be a bad thing either."

Sakayanagi Arisu caught the teasing tone in her father's words and let out a resigned sigh. "Father... are you really that eager to marry me off?"

"Hahaha—"

Sakayanagi Narumori let out a hearty laugh and waved his hand. "While that's not entirely off the table, what I really think is—through this opportunity, Arisu, you can learn something."

He dropped his smile, his gaze turning earnest and gentle. "For instance, compromise and tolerance."

His tone slowed. "I know your temperament best. You're clever, but you're also too willful, too self-willed, sometimes even reckless. With absolute strength backing you, that might carry you through anything, but sooner or later, you'll run into obstacles you can't overcome alone."

He looked into his daughter's eyes and spoke with weight. "Now that someone has appeared who can make you 'rein yourself in' just a little—that's not necessarily a bad thing."

Sakayanagi Arisu lowered her gaze, silent for a moment, then gave a slight nod. "Since Father says so... I'll try my best."

"Mm, that's good."

Sakayanagi Narumori nodded in satisfaction and gently patted her shoulder. "It's getting late. I'll have the driver take you back to school. You have class tomorrow, so don't stay up too late."

"Yes, Father."

Sakayanagi Arisu gripped her cane and turned toward the door.

Just as she reached the threshold, she paused, tilting her head slightly. A flicker of complex light passed through her violet eyes, and she murmured in a voice barely audible to herself:

"Try my best... huh..."

Then she pushed open the door and, beneath the corridor's lights, walked step by step into the depths of the night.

Behind her, Sakayanagi Narumori watched his daughter's slender retreating figure, his gaze holding both affection and a trace of unspoken worry and expectation.

A new game had quietly begun.

And that piece named "Mazumi Mami" was, in a way no one had anticipated, altering the course of the board.