Jin suddenly felt a gaze on him.
Looking to his side, he saw Elsa watching him with a slight pout.
"Uh, Elsa, what do you think of a tool like this?"
It was a transparently forced transition, but Elsa’s pout softened as she spoke.
"Is there any... concern about fires?"
"Yeah, that's certainly a worry."
If laundry were hung over a stove to dry, it wouldn't be an issue while wet. Once it became light and dry, however, a slight breeze—perhaps an updraft generated by the stove's own heat—could cause it to slide off the hanger. If it landed on the stove, a fire would break out.
Jin had heard stories of similar accidents involving old-fashioned convection heaters, making him particularly wary.
"Martha-san, Hanna, what do you think?"
Jin asked the two people who could best imagine the practical benefits of such a stove.
"Hmm, well now, if we had something like that, we might use it for cooking," Martha said.
"Laundry doesn't dry well in the winter, so we hang it inside the house, too," Hanna added.
"I figured as much..."
Jin fell into deep thought.
Silence dominated the room for a while; no one made a sound, careful not to disturb his concentration. Finally, Jin slowly raised his head and spoke.
"It's doable, provided we aren't too greedy for features."
"Oh? Jin, I'd like to hear your idea. I've also thought of something myself," Reinhard said with a smile.
"Right. Well... I thought it would be best if we didn't have to use high heat to warm the room."
Craft Magic: Heat. If controlled correctly, the temperature could be finely tuned. If the temperature was kept below the point of ignition—for example, if the heat generation was capped at around sixty degrees Celsius—fires could be avoided entirely.
"The trade-off is that it couldn't be used for cooking, though."
Most kerosene stoves Jin was familiar with allowed a kettle or pot to be placed on top for cooking, but that was a double-edged sword. The ability to boil water meant there was always the potential to start a fire.
"I see. That's a very 'Jin' way of thinking."
"Tell me what you thought of, Reinhard."
"Sure. I thought we could simply add a function to detect overheating."
Reinhard suggested that the heating should simply stop if it reached a temperature likely to cause a fire.
"That's also an option. The downside in that case would be the higher unit cost."
Reinhard nodded at Jin's critique. "That's true."
"I see. This is all very helpful," Stearena said, looking pleased. "Two plans, each with their own pros and cons. I suppose increasing functionality drives up cost, while lowering cost necessitates limits on those functions..."
"Well, that's how it goes. You can overcome it to some extent with ingenuity, but fundamentally, it's a difficult balance."
It was even more difficult because some functions were contradictory. Preventing fires and allowing for cooking generally couldn't coexist easily. Attempting to force them to work together would inevitably increase complexity and drive up the cost.
"Martha-san, Hanna, which should we prioritize?"
"Let's see. Tools for cooking already exist, so it's probably fine if it can't be used for that," Martha replied.
"Fires are dangerous!" Hanna insisted.
In a sense, the opinions of the two representatives of the common folk were in perfect agreement.
"We tend to clean while the laundry is drying and do the wash while something's cooking," Martha added. "If it's a house where someone is always around to watch it, then maybe being able to cook on it would be fine."
"I see. Martha-san, thank you very much. That was very helpful."
Reinhard thanked Martha. Such perspectives were more than welcome, not only to Reinhard but to everyone else as well.
"...This sort of thing is nice," Beena murmured softly. "Until I met Jin, I was all by myself. After meeting Louis-sama, that changed, but whenever I'm absorbed in magi-craft, I still feel like I'm on my own."
"Beena..."
Jin was momentarily speechless at her unexpected display of vulnerability.
"Ah, I understand," Stearena agreed. "Developing things alone is free and easy, but it can be lonely sometimes. When you want to consult someone or ask for an opinion, not having that 'someone' there is a lonely thing."
"Hmm, I suppose that's how it is. It's likely the same for research," Toa said, casually putting an arm around Stearena's shoulder.
Marcia seemed to feel the same way. "You're right. Being alone... has its good and bad sides... but I think not being alone is better after all," she muttered.
"Uh, let's get back to the topic," Jin said, bringing the conversation back on track before it derailed further. "In that case, considering safety, I suppose we're talking about an air conditioner."
"Air-con?" someone asked, confused by the word.
"Ah. It's short for 'air conditioner.' It's also called climate control. Basically, it's a device that adjusts the air—meaning the temperature and humidity."
"I see, an air conditioner. So, you mean to make it warm when it's cold, and cool when it's hot," Reinhard said, nodding.
Jin confirmed that was exactly right.
"If that's the case, wouldn't it be more efficient if it produced a breeze?" Elsa asked.
Indeed, if the heat source wasn't kept at a high temperature, they couldn't expect much from natural convection. Just like a modern home air conditioner, it would be better to generate a breeze and circulate the air.
"Then for heating, the air should blow downwards, and for cooling, it should blow upwards!"
"Wait, Hanna?"
"Because warm air goes up and cold air sinks down, right? So that would be better!"
"Well, yes, exactly."
Jin was impressed that Hanna had truly internalized her scientific knowledge. He wondered if a modern Japanese elementary school student could have made the same deduction so readily.
After about an hour of discussion, the concept for the portable air conditioner was complete.
Its size was roughly that of a household fan heater. It could switch between cooling and heating; when cooling, the air would blow upwards, and when heating, it would blow downwards. It wouldn't have precise temperature management like setting it to a specific degree, but relative adjustments like "warmer" or "cooler" would be possible. The airflow could also be adjusted steplessly from low to high.
The most significant feature, however, was that it could be supplied at a low price.
Instead of a magi-crystal, it would run on a magi-stone, and one standard magi-stone would last for about a month, assuming ten hours of operation per day.
"To think there's a way to save mana like this."
"Yeah, as expected of Jin!"
"Truly a Magi Craft Meister!"
This was achieved by removing the recoil-cancellation effect from the Breeze magic used for the blower.
To get into the technicalities, normal wind-attribute magic has no recoil. No matter how strong a wind you create, you don't feel any physical pushback from it. This is because a recoil-cancellation effect works automatically. If you remove that effect, the mana consumption is dramatically reduced in exchange for feeling the physical recoil.
The Jet Thruster and Aqua Thruster produced their motive force through this method, and conversely, the force generator was what resulted from extracting only the power to cancel recoil.
But to return to the point—the recoil from something as small as a blower wasn't enough to make the unit move. By not canceling the recoil, the mana consumption was reduced to one-third.
At the same time, by narrowing the temperature range of the Heat and cooling magic, their mana consumption was reduced by half. This would finally make it a magic tool affordable for the common people.
"How about we distribute it to various countries under the Kunlun brand?" Goose suggested.
"Ah, that might be a good idea!" Reinhard agreed.
"Indeed, establishing the Kunlun brand as a mark of reliability might be a very good move," Lishia added.
Whether the Kunlun brand would truly conquer the global market remained to be seen—that would depend on Jin and his companions.
In the meantime...
(Actually, I wanted to popularize the kotatsu, but that's difficult without Japanese-style architecture...)
Jin secretly felt a twinge of regret.