The Demon Lord Is An Angel
Chapter 374: Kinematics

Chapter 374: Kinematics

Kir landed on his back, Amarena’s swords at his throat.

"I almost had you," he said.

"I thought we weren’t holding back," she chuckled. "And you’re right, that trick of yours almost worked." She withdrew and sheathed her blades before offering him a hand. "Too bad I’m too light on my feet."

Their sparring grounds were almost entirely churned mud now, as Kir had focused on slowing Amarena’s speed more than anything else. "I’m not entirely sure about that," Kir said, rubbing his chin after standing.

He was looking at the muddy field, but something was off. He was trying to put his finger on it when Amarena slapped him on the back.

"Still worrying over the foxes?"

"No, it’s not that... I trust Kordia is alright because she said so. And besides, she has the radio."

"Another convenient thing you’ve pulled out of your ass." Kiryu said. "Or mine, rather. You’re welcome for a lifetime of knowledge."

"Thanks," Kir scowled.

He’d discovered that sparring with his generals once a week was a good way to keep in shape while keeping their aggression down, and that more than anything, he felt, was keeping them in line as they contemplated his apparent strengths and weaknesses.

Amarena had refused a role as one of Kir’s generals, an act that had drawn no few challengers of her own. She had to beat a half-dozen captains to be respected enough to be left alone.

Still...

"What’s with that look? If we were fighting for real, you’d have me as soon as you lifted off the ground."

"Yes, but I was hoping to get more insight into your ability. Especially because you said you can still feel it harming you..."

"It’s not as bad as before though. Maybe one more evolution is all it will take," Amarena’s tail flicked the ground aggressively.

"That’s what you were saying before, and yet here we are," Kir sighed. He was happy to have privacy for his sparring match, but it would be obvious to anyone who the mudiest fighter was if he didn’t clean himself with magic.

Wait...

"Rena... What do you know about your mavenry?"

"It makes me faster."

"Yes, but how?"

"Using mana, of course."

"No. What I mean is... what do you think speed is?" An idea started to form, one that could explain the aging effect of Amarena’s mavenry.

"Tsk. Just tell me where you’re going with this," Amarena crossed her arms.

"Where I’m going is somewhere I should have realized the moment you told me about your maven ability. You might not be affecting your ’speed’ at all. You said that your mother told you the price of your ability was because you didn’t understand it, right?"

"I did," Amarena said.

"What if I can help you understand it differently? I just need to do a quick test first," Kir offered.

"What sort of test?" Amarena balked. "I’m getting control of it. I don’t want to break my understanding and wind up worse than I was."

Kir winced. His understanding of mavens was incomplete at best because he dealt mostly with mages. But he knew that mavens advancing their powers could be far more fraught than mages, who did so with a more generalized approach.

"You don’t have to do anything you don’t want to. I want to do this now because I have ideas, but I won’t force you."

"What sort of test?" Amarena repeated herself, her tail lashing a bit. Kir remembered then that she hated repeating herself.

"I just need you to go over there, and then run towards me when I say so," Kir pointed to the edge of the quagmire he’d generated in the forest clearing where they were sparring.

With a slight crack in the air, Rena disappeared and reappeared at the spot he’d indicated.

"Let me set things up, one minute..."

Kir reached for his mana, which even after sparring with Rena still felt like it was roiling beneath his skin whenever he concentrated on it. Like pressurized plasma, seeking release. Working it into a highly wasteful spell, he flattened the mud between them, then carved in several lines at roughly one-meter intervals.

Her transit had been a complete blur, but now that he was setting the stage for a proper experiment...

"Okay, when I say ’go’ I need you to take this path and come to this spot." He looked around and found a nice, flat boulder, which he picked up and placed where he wanted, clearing it with a bit of magic.

"Just on top?"

Kir shrugged. "That would be my preference. Use your speed as much as you can, when you’re ready."

"Alright, I’m ready," Amarena said without moving.

"Go-"

She appeared on the boulder with a crack of air, but more importantly, Kir saw her footprints paced at regular intervals in the soil.

"Alright. Without stepping on the place I cleared, I need you to head back-"

Amarena disappeared and reappeared back at the start.

"-and this time, run to me as you would without magic. As fast as you can." Kir didn’t even pause as he realized Amarena was acting in anticipation of him.

She ran, which was above average in speed than most because of her long legs, before hopping on top of the boulder.

"Now what?"

"One moment," Kir stepped into the mud and checked the depths with his claw. They were virtually the same, which meant that there wasn’t a difference in the force propelling her. The ones made while she was at speed were more widely spread, but the impact on the mud had been the same.

He used this reference as a starting point for his thoughts.

Amarena’s understanding of her mavenry is that it’s based on speed... but this is more like she’s covering more distance with the same force...

And it ages her... so something about time has to be a component.

"Except that’s not how time is supposed to work!" Kiryu protested. "She should be experiencing less time the faster she goes!"

Kir sent his other life a mental nod, a little grateful for his being willing to help defend their mutual understanding of physics. "From what she told us, she just uses normal enhancement magic to perceive fast enough to match her body’s movements... so maybe she is experiencing less time, but forcing herself to experience more... but if there’s no change in the depth of her steps, then there isn’t a change in mass corresponding to her change in velocity..."

Kiryu sent a mental sound like chalk writing on a board. "The amount of observed mass she gains should be next to nothing if she’s not moving at lightspeed. Those little cracks in the are probably her breaking the sound barrier. Maybe she’s unconsciously spending magic to protect herself?"

"That could be it... but I keep feeling like it’s something else. Something consistent with the normal velocity equation but any overage handled through mana is paid for with time that isn’t experienced mentally, but physically. Applied time..."

"Velocity’s gotta go somewhere kid."

"You don’t mean..."

"Position!" Kir shouted suddenly stood. And then it clicked. The thing he hadn’t been able to put his finger on. There weren’t enough footprints in the mud to account for all the movements Rena had been making. When he counted the steps in the mud again, he saw that there were only two from the initial burst of speed.

"Are you going to explain?" Rena asked.

Kir plucked his kisery out of his storage - a reward for Kiryu - and lit up the tobacco inside it while Kiryu

"This is going to get a little weird... but I would like you to go back to the start."

"Alright," she said.

"Good, now close your eyes and start spinning until I tell you to stop." While she complied, Kir pushed off the ground with his wings before shouting "Keep your eyes closed... Stop!".

He came to land in front of Rena, roughly the same distance as to where he’d been with the rock.

"Alright. Turn to my voice."

Amarena grunted and turned. "This better not be some sort of weird sex game. I prefer sweat to mud."

"Keep your eyes closed. Visualize the rock that’s right next to me."

Even behind her eyelids, he could see her concentrating. "Alright. Now what?"

"I want you to use your mavenry to come to the rock."

"With my eyes closed?"

"Yes."

Amarena took one cautious normal step. Then blurred and -

Crack!

With a sound like thunder, she appeared exactly where he’d asked her to. On the rock, only he wasn’t next to it at all.

Kir started to laugh. He cackled at the realization that he had helped Amarena do something knew.

"What the fuck are you laughing about, Kir?" she crossed her arms. "How did you get there so fast?"

"I wasn’t next to the rock!" he said. "You just teleported yourself there!"

"That’s impossible..." Amarena looked around herself. "But I... how?!"

"How’s your mana feel?" Kir asked.

"That was more draining than normal," she frowned. "I thought this was supposed to help."

"Understanding is what helps," Kir replied. "Your mother knew this... and now I understand how to teach you to understand your gift! It’s not just speed! It’s velocity, acceleration, position, and time. The whole damn equation!"

"I think you should get to the point before she throttles you," Kiryu advised.

"The point is," Kir smiled wide, "what I need to teach you is the kinematic equations," he said in partial English.

"Kine-what?" Rena crossed her arms.

"Mostly it’s algebra. But it’s also the same stuff I was teaching Stella on our journey, remember? Calculus."

"I remember her giving me a headache just bragging about it." The scowl faded from Amarena’s face as her whole body slumped. A mournful groan escaped her throat as she held her forehead, the purple gem glistening between her fingers before she lowered her hands with an indignant look. "I hate math. Can’t we just focus on evolving me?"

Kiryu started to laugh.

"Good luck, kid."