In September, while the summer heat still lingered, Roland arrived at the village. Upon seeing the new stove, Roland and Erik could only let out weary sighs.
"……I’m already tired of being surprised," Roland muttered.
"I’d believe you if you told me Jin-san was the Chief Royal Magi Craftman of the royal capital," Erik added.
Despite their astonishment, they purchased the manufacturing process for the stove from Jin and agreed to handle the acquisition of magi-stones. Following their success with flour, Kaina Village had secured yet another way to bring in outside income.
"And one more thing," Jin began.
When he spoke, the two men turned exhausted eyes toward him, as if bracing themselves for another shock.
"No, I was just hoping you’d let me take a look at your carriage—or rather, your wagon, Roland-san."
Roland gave him a puzzled look. "My wagon? Whatever for?" It was a natural question.
"I was wondering if I could make it move more easily," Jin explained.
"Well, if you reduce the load, it certainly gets lighter. But if we do that, we carry fewer goods and lose our profit," Roland countered.
Jin shook his head. "No, that’s not it. I’m talking about a modification to make the wheels turn with less resistance."
He tried to explain, but since neither of them seemed to grasp the concept, Jin decided that seeing was believing. He led the two men back to Martha’s house.
"Oh? Onii-chan, and Mr. Merchant, what are you doing?"
Martha wasn't home, but Hanna was there watching the house. Jin realized this was a perfect opportunity.
"Hey, Hanna. I just thought I’d show them your handcart."
"My handcart? Sure! I’ll go get it right now!" Hanna chirped. She dashed off toward the barn and returned a moment later, pulling the handcart behind her. She was pulling it with one hand while running at full tilt.
Roland and Erik stared, open-mouthed.
"Th-That is quite a sight..."
"She’s so small, yet she’s... incredibly strong, isn't she?"
Their faces were twitching slightly in disbelief. Jin laughed. "Why don’t you try pulling it yourselves?"
He handed the handle of Hanna’s handcart over to them.
"Hm...? What is this? Why is it so light!?"
They noticed the difference instantly. Seizing the moment, Jin explained the concept of bearings and their effects. He lifted the cart to spin a wheel in the air; when they saw it continue to rotate for a remarkably long time, Roland finally nodded.
"I see... I finally understand what you meant, Jin-san. So, you can equip our wagons with these as well?"
"I can. What do you think?"
"I would absolutely like to request that."
They brought the wagon over immediately. Jin set to work, replacing the wheels, axles, and bearings. He even added rubber tires for good measure.
"Um, Jin-san, what is this material on the wheels?"
"Oh, those are rubber tires."
"Rubber tires?"
"Well, just try getting in for a second."
Jin had Roland and Erik climb into the empty wagon and began to pull it himself. The effect of the ball bearings was magnificent; even Jin, who wasn't particularly athletic, could pull the load with ease. The two merchants were also wide-eyed at the significantly smoother ride the rubber tires provided.
"Onii-chan, let me try too!"
Seeing how much fun they were having, Hanna spoke up. Jin swapped places with her.
"I’m super strong!" Hanna cheered, happily hauling the wagon with the two grown men inside.
"A-Ahahaha..."
Roland and Erik were utterly dumbfounded by the sight. The bearings were doing the work, of course, but the visual was still overwhelming.
In the end, they were fully convinced of the benefits: the bearings made the load feel lighter, and the rubber tires made the journey more comfortable.
"Jin-san, this modification is incredible. Truly. Are you certain you don't want payment for this?"
"I am. But in exchange, I’d like you to increase the frequency of your visits to this village."
Roland’s expression shifted into that of a shrewd businessman. "I see. So this is a strategic investment."
"Yes, exactly."
"The performance is certainly enough to convince me. Besides, if the stoves sell well, we’ll need to come back for magi-stones anyway. I understand. It might be difficult to jump straight to once a month, but I will make an effort to visit at least twice every three months."
Jin felt a weight lift from his shoulders; he had achieved his primary goal. However, this time, it was Roland who pointed something out.
"By the way, Jin-san, those round things the children are playing with over there... could those be...?"
Jin looked where he was pointing. A group of children were tossing dodgeballs back and forth.
"Yes, they are. They’re called balls. They’re made of the same material as the tires."
"Hmm. Would it be possible for you to sell those to us as well?"
"Oh, sure. I don't mind."
Jin had discovered that quite a bit of resin could be harvested from the "tea trees" in the forest and had been looking for more ways to utilize the surplus.
And so, it was decided that he would sell rubber balls as well. Since the actual chemical process was too complex to teach, he would provide them as finished goods for now. He started with an order of fifty each: baseballs, handballs, and dodgeballs.
Once the business deals were finished, Erik began to act restless. Sensing the reason, Jin decided to give him a nudge.
"It’s nice and cool down by the Erme River. Why don't we head over?"
Erik didn't need to be asked twice. He followed Jin to the river, and his face lit up the moment they arrived. There, floating in the water in her swimsuit, was Barbara, lounging comfortably inside an inner tube.
"J-Jin-san, what is that thing she’s using?"
"That’s a float. It lets even people who can't swim stay above the water."
Barbara must have overheard them, because she spotted Erik and waved energetically. Erik looked like he wanted to dive in right then and there, but he didn't have a swimsuit. Jin reached into his bag.
"Erik, if you want to swim, there’s a changing shack over there. Here, use this."
Jin handed him a new swimsuit he had brought along just for this occasion. He had suspected things would turn out this way.
"Th-Thank you so much!"
Erik snatched the garment and bolted toward the shack at top speed.
The two of them swam until the sun began to set. As a side note, both of them ended up getting scolded afterward—Erik for failing to help organize the merchandise, and Barbara for neglecting her household chores to play all day.
It was a peaceful afternoon, marking the final days of summer.