"Yes... it was because of learning to control my essence. Awakened possess a rudimentary form of essence control - they broadly enhance their entire bodies with essence, sometimes narrowing the scope down to a particular limb. After learning to do it as easily as breathing, they can become Masters, and naturally transition to a much more targeted, intricate, and efficient manner of using essence."
Her eyes glinted.
"But I've never been an Awakened. I went straight to being a Master. So, learning to control essence was very hard for me... I had to be conscious of every muscle in my body, every tendon, and every bone. It was like learning to walk again."
A corner of Sunny's mouth twitched as he suppressed a smile. He vividly remembered helping her pass these exact obstacles.
Nephis, meanwhile, continued:
"So, I had to go back to basics. Which groups of muscles do I need to enhance to perform the cut in the most efficient and effective way? My hand, my shoulder, my back, my core, my thighs, my calves... everything had to work in harmony to produce the best result. It took a while to become proficient enough in controlling essence to do it right without thinking. And, in the process, I became much more aware of my body. I also got submerged in studying the basics, on a much deeper level than before. Going deeper and deeper."
Sunny looked at her with curiosity.
"How deep are we talking about?"
She smiled, lingered for a moment, and then said:
"Force equals mass times acceleration."
He blinked.
'What?'
"What?"
Sunny had not expected to hear a physics formula. And he only knew that this was a physics formula because Teacher Julius had once thrown a tantrum about his lack of education and forced him to read a bunch of children's schoolbooks.
Nephis smiled.
"That is the basis of swordsmanship - or spearmanship, or any other kind of weapon skill. Fundamentally, it's all about delivering force. The amount of force is dependent on mass and acceleration. Your body is the source of that force, and your weapon is a force multiplier - it concentrates it into a narrow tip, thus making it easier to deliver lethal damage."
She pointed to the sharp tip of her sword.
"Of course, there are more nuances to that. For example, speed does not exist in a vacuum, it is relative to the enemy. Your body also has to borrow from the ground you are standing on. There is balance, centers of gravity, reaction speed... as for the sword itself, there is flexibility, material composition, center of percussion, and so on. There is also soul essence, Memory enchantments, Attributes, and Aspect Abilities to consider."
Sunny was looking at her incredulously, which caused Nephis to shrug in embarrassment.
"Well, anyway. I've been studying the fundamentals - physics, anatomy, Spell studies, and a bit of other stuff - a lot since returning from the Second Nightmare. And slowly incorporating these insights into my swordsmanship. Uh... something like that..."
He tilted his head, a bit dumbfounded.
'That can't be right. How have we gone from "the essence of combat is murder" to "force equals acceleration"?'
So, Nephis had been studying science... to shore up her fundamentals and evolve her swordsmanship? That sounded very strange.
But the result was apparent... she had clearly improved by leaps and bounds since her Ascension.
Sunny shook his head in disbelief, and then threw a pointed look at her.
His voice was incredulous:
"...Care for a spar?"