February 8th is Hanna's birthday.

It was snowing from the morning in Kaina village, but Hanna's birthday party was being held at Martha's house.

"Happy birthday, Hanna!

"Thank you, Grandma."

"Happy birthday, Hanna."

"Thank you, Grandma."

"Happy birthday, Hannah."

"Happy birthday, Elsa, thank you."

"Happy birthday, Hannah."

"Happy birthday, Auntie Meane, thank you."

"Happy birthday, Hannah."

"Happy birthday, Auntie Reiko, thank you."

The guests of honor are Hanna, her grandmother Martha, Jin, Elsa, Meene, and Reiko.

In case you are wondering, the children of the village came to the celebration in the morning.

In the afternoon, it was Jin and the others.

Everyone chats happily while cutting the cake made by Elsa and Meane and toasting with Citran juice.

"Hannah is 11 years old, isn't she?

Jin mutters. I noticed that she was taller than Reiko.

"Hannah, how are you getting on with your studies?

Elsa asked.

"Yes!　The old man is teaching me a lot of things. I have already memorized the formula for the quadratic equation.

"That's great, Hannah."

That means she has already mastered the mathematics at the junior high school level.

In addition to her natural spark, Hanna is learning scientific knowledge from the basics. We look forward to her future.

"If a school is built in <>, I want her to attend it.

Jin mutters to himself.

It is like a parent's heart that wants to develop Hannah's talent.

"If she wants to go there, she can use the warp gate.

"Brother Jin, I don't think so."

Erza warned Jin, who always forgets to put his own weight somewhere when it comes to Hanna.

"Then we'll get a special plane ......."

"That's a bit of a stretch."

"I see."

Hannah giggled at the sight of Jin.

Outside the window, snow was fluttering.

"There seems to be a lot of snow this year.

Jin said, "There is a saying that a year with a lot of snow brings a good harvest.

"Brother Jin, why is that?"

"Well, I don't know. ......I think, in my country, rice is the main crop, and it needs water. When there is no water in summer, it is called and it causes a bad harvest. So, if we have a lot of snow, it means we don't have trouble with water. ......?"

"But once the snow melts, won't it last until summer?"

"Yes, because the high amount of snow on the plains means that there is a lot of snow in the mountains. So, the snow on the mountains will melt slowly and become groundwater or subterranean water to moisten the foothills. ......

"Hmm, that makes sense."

"The country where your grandmother was from is amazing!　Isn't there any other legend like that?"

Erza was convinced and Hannah was interested.

"Hmmm, I guess so. ......"

Jin recalled a story that his science teacher had told him in junior high school in a chatty manner.

"When a dragonfly flies high, it's sunny, and when a swallow flies low, it's raining.

Jin adds that both dragonflies and swallows are types of birds.

"Well, when birds fly high, it means there is an updraft. And when they fly high, there is a lot of sunlight, so it is sunny. Does that mean it's sunny?"

Hannah makes a surprising guess.

"That's what I think. And swallows, birds that eat insects, don't fly very high when rain is near and there's a lot of humidity in the air, so I think it's ......."

"That's interesting!"

"That's interesting!" "That's what the ancients have been telling us from their experience. I think it's called <>."

"We have it in the village of Kaina. Uh, was it sunny in the morning when the birds are chirping, Grandma?"

"That's right. Yes, and also that it rains when you hear a distant sound.

Hannah explained and Martha added.

"What do you mean by the birdsong ......?"

Jin thinks about it for a moment.

"Brother Jin, on sunny mornings, it gets light earlier, so it could mean that the birds wake up .

When it's cloudy, the birds wake up at different times, Elsa says.

"Yes, that may be so.

Jin nodded.

What about distant sounds?

Jin had an idea.

"Probably because sound waves are bent."

"Oh, refraction!"

Hannah shouted as if she understood.

"When the air density on the ground is high and the air density above is low, sound waves are bent, right?

"That's right. And when a low-pressure system is approaching, warm air will flow into the sky.

"I'm sure that's true."

It's the same reason why, on winter nights, when the ground surface is cold, we can hear distant sounds better.

"Hannah, you're amazing!"

Meane rolls her eyes.

"No, I'm not. It's all book knowledge."

Reiko speaks softly to Hanna, who is still modest.

"No, Hannah. No matter who you are, no matter how smart you are, knowledge alone is not enough. There must be to use knowledge properly. And Hanna-chan has it."

"That tickles, Reiko!"

Reiko praised her, and Hanna fidgeted. The gesture was so cute that it made everyone feel relaxed.

"Oh, that's right. Can I open what you gave me?"

Hannah said shyly, and everyone nodded.

"Uh, this is from your grandma. ...... Oh, a watch!"

Hannah's own pocket watch. It has a mithril silver chain so that she can wear it around her neck.

"I'm sorry about last year."

Hannah smiles at Jin as she apologizes.

No, it's okay, you're busy. Besides, you remembered me this year."

Next Hannah opens the gift from Elsa.

"Oh, a doll!"

It was a doll made by Elsa. Of course it is for decoration, but inside it is an air-purifying magical device that removes dust and even sterilizes the doll lightly.

"Thank you!

"When we sleep, we tend to be vulnerable to disease.

It's also for Martha's sake. Hannah was glad to hear that.

"Oh, it stopped snowing.

Elsa muttered as she looked out the window. Everyone looked out the window with her.

Against the blue sky that was beginning to peek out, we could see silvery white mountains.

"Spring is coming soon, isn't it?

Martha muttered.