Jin explained just how inefficient it was to attempt moving water with wind-attribute magic.
"……In short, the size of the 'molecules' we’re targeting is different. Water molecules are several times larger than air molecules; the difference is like sand compared to gravel, so to speak."
The term "water molecule" as Jin used it here lacked scientific precision. The size of a single water molecule (H2O) is not significantly different from an oxygen or nitrogen molecule. If anything, it is lighter.
The reason waterproof breathable materials allow water vapor to pass through but block liquid water is that in liquid water, the molecules do not exist as individual H2O units, but rather as groups of several or dozens of units called "clusters." This function relies on the fact that their apparent size is larger.
In other words, the holes are large enough to let individual gaseous water molecules pass, but small enough to block the clustered liquid water molecules.
Water-attribute magic acts upon these clusters, but wind-attribute magic acts upon each individual water molecule within the cluster. Simply put, it is extremely inefficient.
Acting on them individually does not increase the power either. It is quite literally a waste of effort.
Digression aside.
By using metaphors and real-world examples, Jin succeeded in convincing the group, who lacked basic knowledge of atoms and molecules.
"……No, Jin-dono, I appreciate the explanation. To be honest, there were parts I didn't quite follow, but I believe I understood the two most important points: the Wind Thruster can be used even if it gets submerged, and doing so will increase mana consumption. I think I’ve got that much down."
Christoph expressed his gratitude. The others nodded as well, their faces looking a bit weary.
Since it was a good stopping point and they were nearing the end of the day, the first session came to a close.
"I apologize for the delay in the announcement, but we have prepared accommodations for everyone."
Led by Christoph—or rather, with everyone naturally walking in the same direction—they headed toward a hotel built by the lakeside. It was a cozy establishment with a pleasant atmosphere.
"The government has chartered the entire building until this project is finished."
Everyone, from the site manager Christoph down to the guard soldiers, would be staying at this hotel.
Each person was assigned an individual room. The rooms were on the second floor, arranged in order: Reinhard, Jin, and then Elsa.
All the rooms faced Lake Wasu and offered a fine view.
"Hmm, two rooms—a living room and a bedroom."
Jin set down his luggage and looked around. Reiko was already busy inspecting the interior for safety.
"Father, it has its own toilet and shower room."
Perhaps because water was abundant so close to the lake, the facilities were quite good. However, Jin still preferred a large communal bath.
He decided to grab a change of clothes and head to the bath. On his way out, he ran into Reinhard and Elsa in the hallway.
"Ah, heading to the bath too, Jin?"
"Yeah, that's the plan."
"Me too. Shall we go together? Elsa, you can walk with us as far as the entrance."
"Mm."
Since the baths were separated by gender, Elsa accompanied them down to the first floor where the facilities were located.
"Oh, this is quite spacious."
"The southern part of the Shouro Empire has a culture of bathing. While it's not a hot spring, it's still relaxing."
There were no other guests, so Jin and Reinhard essentially had a private bath. The two of them soaked in the hot water, stretching out their limbs.
"Hey, what do you... think of Rodrigo?"
Taking advantage of their privacy, Jin spoke to Reinhard.
"Hmm, he seems like a decent enough man."
"That's not what I meant."
"……You mean his potential connection to Marcia, right?"
Marcia was Jin's partner back during the Golem Boat Race in Port Rock.
"……I can't help but think he might be her father—the one she said went missing."
"I suspect the same."
Reinhard had also heard about Marcia's circumstances and was aware of the situation.
"……I wonder what we should do."
"It depends on how the man himself feels about it."
"Shall we wait and see for a bit longer?"
"……Yeah, that might be for the best."
At that moment, they heard the sound of someone entering the changing room, and the conversation came to an end.
Meanwhile, there was already someone in the women's bath.
"Ah."
"Oh.……You're Elsa-san, right?"
It was Kleia.
"Good work today."
"Hehe, honestly. I'm exhausted after just the first day."
Kleia laughed as she washed her body. While rinsing herself, Elsa glanced at her out of the corner of her eye.
Despite Kleia's short stature—she only reached about as high as Elsa's nose—she had a fairly generous chest, which made Elsa feel a slight sense of unfairness.
As Elsa soaked in the water, Kleia finished washing and joined her.
"Ahhh, a spacious bath really is the best."
Kleia's sigh was directed at no one in particular, and Elsa replied with a soft "Yeah."
"Are you very knowledgeable about ships, Elsa-san?"
"Eh, yes.……Because I entered the Golem Boat Race in Port Rock."
Kleia seemed surprised by those words.
"Wow! That's amazing. I've heard rumors about that race. I heard it draws the most prominent engineers from the Kingdom of Elias."
"I suppose so. I was on a team with Rai-nii…… my cousin, Reinhard."
"Eh?……Ah, I see. I thought it was unusual for you to share the name Randol, but you're cousins.……So, what is your relationship with Jin-san?"
"……With Jin-nii……"
Elsa was momentarily at a loss for words. The other day, she felt like her feelings alone had reached Jin…… or so she thought. And immediately after that, in a moment of crisis, Jin had hugged her. She had even received a ring.
However, she hadn't heard Jin's own feelings on the matter yet.
"……I am his top disciple, and sister-in-law."
As of right now, she lacked the confidence to say anything more.
"Whoa, his top disciple! Of the Magi Craft Meister!"
However, Kleia latched onto the "top disciple" part with enthusiasm.
"He was incredible today! That speed of Forming! That accuracy! And his knowledge is just immense. He really is the world's only Magi Craft Meister!"
Kleia was full of nothing but praise for Jin, her voice filled with respect. Listening to her, Elsa felt a complicated mix of pride and a hazy, restless frustration in her heart.
"I need to wash my hair."
In an attempt to change the mood, Elsa got out of the water. Kleia followed her out.
"Oh, I'll wash your hair for you. Come on, let's wash each other's!"
"Eh?"
Despite this being their first real meeting, Elsa found Kleia's forward personality a bit difficult to handle.
However, she couldn't bring herself to say it to her face.
"……It's fine. I'll wash it myself," was all she could manage, but...
"Oh, don't be shy. The hair-washing liquid they have here is actually quite good, you know?"
Ignoring her protest, Kleia moved behind Elsa and poured warm water from a pail over her head.
"Keep your eyes closed tight, okay?"
While saying that, she applied the hair-washing liquid to Elsa's head.
"Alright, here I go~"
Then, with hands that were gentler and more careful than expected, she began to wash Elsa's hair.
"Anywhere itchy?"
"……Mm."
Elsa was already helpless to do anything but go with the flow.
"You have such beautiful blonde hair. It's so straight and translucent. I'm so jealous; my hair is just this coarse red stuff."
After she finished washing Elsa's hair while chatting away, she added, "I'm going to rinse it now, so don't open your eyes yet," and washed away the soap with water from the pail.
Until now, the only person who had done this for her was Mine—her maid, nurse, and biological mother—but Elsa's impression of having Kleia do it was that it was "surprisingly not bad."
"T-Then, now, it's my turn."
"Oh, thank you!"
Though her movements were unpracticed, Elsa was reasonably dexterous and washed Kleia's head just as it had been done for her.
The hair was indeed stiff, but it was well-maintained and clean.
"Ahhh, that feels so refreshing. Thanks."
After thanking Elsa, Kleia headed back to the bathtub.
Elsa then washed her own body and entered the water once more.
Kleia seemed to enjoy long baths and was still soaking.
"……Hey, do men prefer girls with blonde hair?"
"……Pardon?"
Elsa was hit with a question that felt incredibly difficult to answer.
"I have this red hair, you see, so I get so jealous when I see girls with blonde hair."
"……I know someone with red hair who became a countess," Elsa said, remembering a friend in the Kingdom of Egerea.
"Eh! Really?……Hmm, then is it the chest? I wonder if it's the chest after all?"
"……There isn't much difference between us."
After saying that, Elsa felt inexplicably dejected for some reason.
"Hmm…… then maybe it's the face after all……"
Unaware of Elsa's inner turmoil, Kleia mused innocently to herself.