Their speaking speed was very fast, with professional terms emerging one after another.
One would propose a hypothesis, and the other would immediately provide a method for verification or correction.
Yushiro was sweating profusely recording by their side, often unable to keep up with their speed of thought.
Himura Ruri huddled in her chair, watching with wide eyes.
Those "energy spectra," "gradients," "control groups"... she didn't understand any of it, but she could feel the focused atmosphere of Mr. Cheng Mo and Lady Tamayo's complete immersion.
She saw the faint golden glint occasionally flashing in Mr. Cheng Mo's eyes, and Lady Tamayo's fingers trembling slightly from excitement.
Though she was scared of this environment, she was filled with awe and gratitude for Lady Tamayo's research that could help her father.
Life underground had no distinction between day and night; only the laboratory lights were constantly on.
Time flowed by in data recording, sample analysis, and intense discussions.
Occasionally, Tamayo would gently call Himura Ruri over to draw a small tube of blood.
The young girl would try her best to suppress her fear, extend her arm, but her eyes would look towards Cheng Mo, as if seeking courage.
Cheng Mo would usually give her a calm look, and she would feel less afraid.
Tamayo would also ask her to record whether there were subtle changes in the color of her father's statue in the observation room, or ask if her father had experienced similar periods of slumber before.
Himura Ruri would always try hard to recall, then answer seriously, word for word, afraid of missing any detail.
Whenever this happened, Yushiro would stand not far away, staring intently at her, as if she might suddenly lash out and harm Lady Tamayo at any moment.
Himura Ruri could feel his gaze, and though she was scared, she could only try to ignore it and focus on her own tasks.
She didn't understand why this young man held such animosity towards her, but she didn't want to cause trouble for Mr. Cheng Mo.
Cheng Mo and Tamayo's research meetings lasted for a long time every day.
Himura Ruri would stay quietly, listening to the profound terminology and watching the precise instruments and flashing lights.
Gradually, she was no longer so afraid of this underground world, and even began to vaguely understand that her father's strange condition might truly find hope of turning back into a human here.
The careful and intelligent girl gradually picked up on a pattern.
She would take advantage of pauses in Cheng Mo and Tamayo's discussions to quietly ask if she could use the kitchen.
After receiving permission, she would go to the small, but surprisingly well-equipped kitchen, to prepare simple meals for herself and Cheng Mo.
She knew Mr. Cheng Mo wasn't picky about food, but she still tried her best to make it better each time; this was the only thing she could do at the moment that felt like "repayment."
Sometimes, she would run into Yushiro.
Yushiro was always meticulously preparing tea and snacks or special "medicines" that Lady Tamayo needed, his movements precise, his expression as focused as if he were performing some sacred ritual.
When they met, the air would instantly cool.
Himura Ruri would immediately lower her head and quicken her movements, wishing she could shrink into the wall.
Yushiro would let out a very soft, contemptuous snort from his nose, looking at her as if she were a dirty mouse that had wandered into a sacred hall, full of vigilance and annoyance.
They never spoke, as if the other were transparent, with only cold silence pervading the small kitchen.
Once, as Himura Ruri was carrying soup, the floor was slightly slippery, and she was also a bit tired from days of mental strain.
Her wrist trembled, and the hot soup was about to spill, the bowl on the verge of slipping from her grasp.
"Ah!"
She let out a short gasp, her face instantly paling with fright.
The young girl wasn't afraid of scalding herself; she was afraid of making a loud noise that would disturb the adults in the adjacent lab, and even more afraid of wasting food.
Just as the bowl was slipping from her hand, a figure flashed over with extreme speed.
Yushiro, with a sour expression, moved astonishingly fast, steadying the nearly shattered bowl with one hand.
With his other hand, he pulled out a rag from who-knows-where and swiftly wiped the spilled soup clean, leaving only a small damp mark on the floor.
The entire process made almost no sound.
"Clumsy! Impetuous human!"
Yushiro lowered his voice, glaring at her fiercely, his tone extremely sharp.
"What if you make noise and disturb Lady Tamayo?! You can't even do this small thing well!"
Himura Ruri, still shaken, looked at his quick and decisive movements and his even uglier expression, standing there at a loss, her cheeks burning red, mumbling, "I-I'm sorry..."
"Hmph, hurry up and finish, you're in the way!"
Yushiro gave her another disdainful glance, and only after confirming that no stains that might attract attention were left, did he pick up the much more exquisite tray of tea and snacks he had prepared for Tamayo.
He walked out carefully, as if guarding some precious treasure, as if another second there would be unbearable.
Ruri watched his retreating back, then looked at the quickly wiped-dry mark on the floor, her mind in a jumble.
This person... he clearly disliked her so much, so why did he help?
Perhaps... he really was just afraid of disturbing Lady Tamayo.
She silently composed herself, and with even more care, refilled the soup and carried it out.
During breaks in his research, Cheng Mo would take very short moments to check Himura Ruri's physical condition.
His fingers rested on her slender wrist, and a faint, almost imperceptible trace of Chakra probed in, quickly circulating once.
"Your Qi and blood are a bit more stable than yesterday; Qi Refining Technique breathing is... practiced, with the best effect."
He withdrew his hand, giving instructions in a flat tone, never saying an extra word.
Himura Ruri quickly nodded, trying hard to remember every word.
Mr. Cheng Mo's words were always precise, cutting straight to the core.
Occasionally, and very rarely, Cheng Mo would linger for a moment longer after his check-up.
Looking at Himura Senichi's crystal statue in the lab, he would, in his uninflected tone, speak of more profound things.
"Your father's battle is not external; it is internal."
Cheng Mo pointed to his own head, then to his heart.
"The erosion of demon blood is not only physical, but also a pollution of the soul and will. His willpower is strong enough, which is why he has been able to constantly fight against that pollution."
Himura Ruri held her breath, trying hard to understand every word.
"Soul... will?" she murmured, repeating the words.
These terms were too profound for her.
"It can be understood as the most core 'self.'"
Cheng Mo, uncharacteristically, offered an explanation.
"A sufficiently strong 'self' can resist external distortion; your father is doing exactly that."
Although she still only half-understood, Himura Ruri's heart warmed.