The duo talked about visiting a human city, and they had slightly different opinions about it. Fen wasn't a fan because he's not fond of them, but he didn't stop her, either. Having gone to bed early, Sophia wasn't nearly as sleepy as the day before. It still took some work of the wolf to wake the girl, though.

"Morning, Fen..."

"Yes, good morning. Want some breakfast?"

"Nah, I'm good. I'll just get some, uhm, what was it again… Right, laspberries later on."

"I see. What do you want to do today, Sophia? Get started on nature magic or-" He tried to divert her attention regardless.

"Can we cover some ground today? I am interested in the magic, but I don't feel like I would be able to concentrate at the moment…"

"Let's do that, then. Yes, you need to be able to focus properly."

"Okay, thanks."

----------------

After Fen had his usual breakfast and Sophia gathered some berries as a snack, the two got going. They simply kept advancing towards the human city with tremendous speed while having nothing to talk about. Running all the way into the late afternoon, Fen and Sophia finally decided to take a break, not because they were tired, but it became too dull to continue.

"How about food now, Sophia? You must be hungry after all this running.

"Yeah, you're right… It feels like I burned a million calories today."

"Good. Let's see, vegetables around here-"

"Ah, no, don't bother, Fen."

"Hmm?"

"Meat. I want to eat about a ton worth of protein. Having worked out all day, I have a serious craving for protein."

"Oho! So, you've finally accepted the greatness of meat, huh? Splendid! That's perfect! There are actually some kows around. Let me get them really quick."

"Ah, can I give it a try, Fen? Aside from the huge bird… thingy I accidentally killed because it surprised me, I have yet to fight anything."

"Hmm? Sure, I don't mind. Can I come with you? I'm interested in how you'll hunt them."

"Of course. They are-, it's these three dots about 300m behind those trees on our left, right?" Sophia used her detection magic to scan the area for fitting respondings.

"Exactly." Having confirmed the target, the two carefully sneaked towards their prey.

"Let's see," While hiding behind some bushes, Sophia was thinking about a way to defeat them. "Can I play around a bit?"

"Be my guest."

"Okay, let's trap them first." Saying so, the ground below the kows started to rumble. Before they could even react, the earth split open, and they fell into the newly created hole.

"M-Moo…" The hole wasn't deep enough to kill them because there could still cries be heard from the animals.

"Well, I could've killed them, but because they pose not the slightest bit of threat, I kinda want to try a thing or two."

"I get you! I so get you, Sophia! Playing around with your prey because the power gap is so enormous brings me, too, great joy."

"What now? So many options… I could close up the hole, letting them suffocate… Push the walls together, flattening them… Fill the hole with water, drowning them… Setting the hole on fire, grilling them."

"M-Moo…" A pitiful cry came out of the hole. The trapped prey seemed to be aware that their end was imminent.

"Sophia, please remember that we're planning to eat at least one of them. Some of your ideas, as fun as they sound, wouldn't leave much usable food behind.

"Ah, you're right." Sophia noticed the mistake in her ideas. "Oh, there's something I wanted to test when I was learning air magic. Might as well give it a try now." Closing her eyes, she focused on her concentration.

"Hmm?" Fen seemed interested in what she was up to.

"Air-, How was the composition of air again? Was it 20%...? Close, I think it was around 21% oxygen, right? Almost the entire rest was… nitrogen with a tiny amount of other gases like argon and carbon dioxide, but let's not care about them for now. I'm fairly sure the air in this world's roughly the same. It at least feels like that. Okay, let's try to eliminate the oxygen inside the hole. I think you usually die after a short while when it falls below 10…? Or was it lower than 8%? Well, whatever, let's just get rid of as much as possible!"

"Sophia?" The wolf, having never heard about most of these words, was obviously confused about her mutterings.

"Shhh, I need to concentrate here, Fen."

"S-Sorry…" He didn't mean to disturb the girl.

"Let's continue-" Regaining her concentration, she tried some things out until she found her answer. "Oh, I think it's working!"

"What is?" He still didn't understand.

"Mo… MoOoo…" Some cries came from the hole, but they were becoming increasingly inaudible until it became completely silent. Shortly after, three thuds could be heard as the kows fell to their side, still slightly twitching but dying shortly after.

"W-What did you do, Sophia?" He tried to get closer to the hole to take a look, but she stopped him.

"Don't go there yet, Fen. It's dangerous… even for you." About a minute passed before Sophia walked up to the hole. "It's safe now."

"O-Okay…" Joining Sophia, he looked down and saw the dead kows without having any wounds whatsoever. "Uhh, what did you do?"

"Err, how to explain… Fen, do you know what air is?"

"Air…? Air is air…" His expression basically said 'what is this girl even talking about' as he didn't understand her question.

"Ah, so it's really unknown in this world… Air or the atmosphere is actually a combination of many different things. Fire, for example, doesn't use the air as a whole to burn, but a gas we called oxygen in my old world. Once the oxygen concentration gets too low, the fire dies as well. That's what usually happens with fires in a closed room. Well, the oxygen gets replaced or converted to some other gases, but that's not… that important right now. I-It’s not because I don’t really know how it actually works or anything…"

"A-Alright?" He could barely follow her.

"It's the same for living things. Once the oxygen level in the air gets too low, they die. Actually, for them, it's even worse. While fire mostly cares about having enough oxygen, when the percentage of certain gases in the air change too much, living beings can get poisoned by merely breathing the air itself.

"Hmm…" Fen was trying to understand the concept. "So… air's basically a mixture of things…? Changing this mixture can kill us?"

"More or less… But that mixture, except for the oxygen being too low, has to be off by quite a bit. Else, it would only slightly harm you, or at best, kill you in a very slow yet agonizing way. That way of dying would be way worse than your standard run-of-the-mill suffocation because you can still sort of breath, though. It can't keep your body functioning, letting you die bit by bit over the course of maybe even hours."

"S-Sophia, you can be quite scary… Even I would be reluctant to use such a method."

"How rude!" She didn't like his accusation. "The kows died really quick, didn't they?"

"Now that you mention it, it was about the same time as suffocating someone, no, even faster than that. What did you do then?"

"I got rid of the oxygen part in the air, letting them suffocate basically in an instant."

"Ah, that's how it is."

"Well, suffocating them the normal way would've been much easier, but I wanted to try it…"

"Yes, you apparently did something quite… no, really outrageous, judging by the magic power you poured into this idea of yours."

"Yeah, it was super hard to… keep the oxygen out. Thanks to that, I'm even more hungry now… Fenny, I leave the rest to you~."

"This girl…" Doing as requested, he gathered the corpses and began preparing their meal. It was hard to decide whether it was a late lunch or an early dinner, thanks to the time being right in between. Because of that, there was still quite a bit of day left once the two finished eating.

"Haa~, that was a good meal, thanks for that, Fen." Rubbing her stomach, Sophia looked satisfied.

"That's the superiority of meat for you." The resident carnivore was smug. "What now? Want to keep going a little longer?"

"No, I think we covered enough ground for today…"

"You're right. We made way better progress than I thought we would already. Even if we don't keep going, I would reckon that we could run into the first humans around the same time as now tomorrow."

"Is that… so?" Sophia somehow seemed much less enthusiastic than he thought she would be.

"Is something the matter? You were all over the place today already, and now you're back to being down."

"I was thinking a lot, and now I'm kinda worried…"

"Worried?

"Yeah…" After being urged to, Sophia eventually opened up to the wolf, and the two had yet another little conversation of theirs where she let off some steam.