"Jin, look at this! It says 'mercury'! That's rare!"
Saki, who had been scouring the catalog, shouted out in surprise.
"Mercury?"
Jin was equally startled. While they used mercury thermometers on Capricorn 1, he hadn't seen the substance anywhere else except for Hourai Island.
He wondered if the production sites were limited, or if people simply didn't know it existed yet.
It was likely both, Jin thought.
Mercury was the only metal that remained liquid at room temperature. It was primarily produced as cinnabar, a sulfide, or as native mercury in its pure elemental form.
Because it could dissolve gold and then be evaporated away with heat to leave the gold behind, it had been used for gilding in ancient times. However, this method produced toxic vapors and caused heavy metal pollution, so it wasn't used in the modern era.
While metallic mercury had a high boiling point, air saturated with its vapor could contain several times the amount necessary to be toxic. One had to be extremely careful.
Jin knew at least that much from his past experience working with metals.
"I wonder how they use it here?"
He hoped it wasn't being used in a dangerous manner.
"Also, this caught my eye. It says 'alum'."
"Heh."
They said that different places produced different things, but the region west of the Harihari Desert certainly offered a unique environment.
"When I think of alum, I think of adding it to pickles to keep the eggplants purple, or using it to suppress body odor..."
It was the sort of practical knowledge one might find in a grandmother's bag of wisdom.
Since aluminum seemed to be scarce in this world, alum—which contains aluminum—should have been considered a rarity. In Jin's original world, it was synthesized chemically, but until recently, it had been mined in places like the Myoban hot springs in Beppu.
It seemed it was being collected here in Mitsuho as well.
"Apparently, they use it for dyeing."
Cotton was the primary fabric for clothing here, so they likely used the alum as a mordant to set the colors. Jin only knew the basics, but Saki was clearly intrigued.
"I definitely want some of this alum!"
Other items that piqued their interest included ethyl alcohol and wood vinegar.
"Hmm... I’m becoming more convinced the magus was from my home world, and that he was someone with a strong background in chemistry."
The mystery continued to weigh on Jin’s mind.
"But..."
There was one contradiction that bothered him.
"It doesn't seem to connect to magi-craft."
Assuming Shuuki Tsetse was related to Adriana Barbora Tsetse, the skills seemed mismatched.
In Jin's mind, Shuuki Tsetse specialized in chemistry, while Adriana Barbora Tsetse specialized in magi-craft. Considering Adriana had lived alone on what was now Hourai Island, it was highly likely that Shuuki Tsetse was the older of the two.
If he was her father, then the lack of chemical knowledge in the legacy Adriana left behind felt strange.
"...I still don't have enough information."
It was like a puzzle with missing pieces; the full picture refused to emerge.
"I wonder if something was left behind in the northern lands..."
The north continued to beckon to him.
The night proceeded peacefully.
After eating dinner and taking a soak in the hot spring, everyone gathered to chat.
"Jin-nii, I borrowed this."
Elsa, the last to return from the bath, held a small box in her hand.
She explained that while passing through the lobby, a staff member had recommended it as a local game. She had accepted it on the spot, forgetting to even ask how it was played.
"Let me see."
Jin took the box from her.
"...Hanafuda?"
He had expected playing cards, but it was a Hanafuda deck.
He laid out an extra zabuton and scattered the cards across it. The designs were simplified, but they were definitely Hanafuda cards. Having been taught by the Orphanage Director, Jin remembered all the rules.
"...Though the artwork looks like it was drawn from memory."
Was this, too, something the magus had introduced?
Hanafuda was a Japanese card game dating back to the Edo period. It used seasonal themes for each month from January to December to represent numbers 1 through 12, with each month consisting of four cards of varying values.
(I think there was a theory that it was created because the Shogunate banned gambling with foreign cards...)
Regardless of the origin, Hanna was watching with sparkling eyes, so Jin decided he had to teach them. He began his explanation.
"The cards are divided into twelve months based on the pictures. First, you need to learn those. January is Pine, February is Plum, March is Cherry Blossom..."
"Hehe, I see. That’s why they're called 'flower' cards, then?" Saki said, impressed.
"Jin-nii, the August 'Baldy' and the November 'Rain' aren't flowers, are they?" Elsa asked, voicing a common observation.
"Ah, August is technically pampas grass, but the moon is the main feature. In my home, the moon is sometimes colloquially compared to a shaven head. And November is likely willow, but the rain is more iconic," Jin explained. "I’m not a total expert, though. Now, the cards are worth twenty mon, ten mon, five mon, and then the junk cards. You'll need to memorize those values as well."
"Got it! I remembered them!"
Hanna was the first to catch on. Elsa and Saki followed shortly after.
"Alright, let's try a simple game of Bakappana first. It's played with 'seven in hand, six on the table'..."
Jin went through the rules step by step.
"If there are four people, you decide in order from the dealer whether to play or fold. Ultimately, three people play. The dealer gets to match cards first, followed by the nakaya, and finally the bike."
He was teaching them the specific local rules and terminology he knew.
"You flip a card from the deck in order, and if the month matches a card on the field, you take it."
"...Shall we try a round?" Elsa suggested.
Thinking it would be easier to learn by doing, Jin looked at everyone's hands and guided them while the three women played a practice match.
"Mm-hmm, I think I've got it. So, if there's a card on the table that matches one in my hand, I take it. If not, I have to discard."
"...And then you flip a card from the deck, and if that matches something on the table, you get those too."
"Exactly. You're all quick learners. Let's try it for real, then."
"I win! Let’s see... eighty-five points."
"Hanna, in Hanafuda, we call them eighty-five mon. Since I’m the nakaya and I have eighty mon, and Saki is the bike with seventy-five, she loses five mon to you. That means it’s Hanna’s tan-gachi."
"Jin-nii, what’s a 'tan-gachi'?" Elsa asked.
"Ah, sorry. Look at the five-mon cards—they all have tanzaku, those paper ribbons, drawn on them. So, the five-mon cards are often called 'tan.' That makes a win by ribbons a 'tan-gachi'."
"...Interesting."
"Alright, Hanna is the dealer now. Mix them up and deal them out."
"Okay!"
The cards were a bit large for her small hands, but Hanna skillfully shuffled and dealt them out in the seven-and-six format.
"Alright, I won't lose this time!" Saki declared.
"...Saki-nee, I won't lose either," Elsa added.
"I'll fold this round. You three go ahead."
In the rules Jin was using, the right to fold passed from the dealer down to the bike. If the dealer stayed in, the next person could choose to fold.
"There! Take that!"
"Oh no! Hanna-chan, you took the card I wanted!"
"...An oki."
"Elsa, you've got good luck with those okis."
An oki occurred when a player flipped a card from the deck that happened to match one already on the table.
"...This time, I win by twenty mon."
"Ugh, next time for sure! Elsa, hurry up and deal!"
They played on, completely losing track of time as they became absorbed in the game.
"Elsa-sama, it is morning. Please wake up."
The sound of Edgar's voice brought Elsa back to consciousness.
"...So sleepy."
Rubbing her eyes, Elsa sluggishly sat up in her futon. She was suffering from a bit of sleep deprivation after playing Hanafuda well past midnight.
"Saki-sama, please wake up."
"...Mnn... just a bit more..."
Beside her, Saki was trying to hide under her futon to sneak in a second nap.
"Onee-chan! Saki-sama! It's morning!"
Only Hanna, who had fallen asleep long before midnight, was perfectly rested and full of energy.