Chapter 1: Water Bullet

Chapter Four: Age of Sorcery
Dragon Era 900
Carriages rattled along the paved road. The horses pulling them looked so much like creatures from Earth that I couldn’t help turning to look back after one passed.
On closer inspection, they had six legs. So close.
Aside from the horns, they would’ve been perfect.
Still, with six legs, I found myself oddly impressed they could walk without tripping.

The carriages all looked much the same, but the horses pulling them were wonderfully diverse: some had little wings, some were covered in scales, some had long snake‑like tails. I even saw one with two heads. Would you call that a two‑horse team…?

Following the street on and on, I saw windmills in the distance. That, too, was a slightly odd sight. Long ago now, in my Earth memories, windmills were built all facing roughly the same direction in rows.

But the windmills ahead formed a ring, each set at a slightly different angle—and a girl in white was circling around them and around, whipping past in flight.

「Hey, Sylph. Thanks for your work today, too.」

When I called out, Sylph waved happily and sped up. The ring of windmills was a circuit set up so she could keep them turning without stopping. Each time she looped around the mills, their vanes whirled and fed power into the shafts.
In that millhouse, little folk about a meter tall—house spirits, Brownies—were carrying in sacks of wheat.

「Ah, Sensei!」

Going past the mill and farther out, I spotted a gigantic girl sitting down. A tiny pixie was perched on her shoulder.

As close as ever, the two of them—Ruful and Tia.

「Huh? What are you two doing here?」

That said, they’d normally be working separately at this hour.
Ruful does civil works and construction. Tia teaches at the elementary school.
The combo of Ruful, who builds even bigger houses and roads with her huge body, and Tia, who guides tiny children with her even tinier body, is a minor attraction even in Hiiro Village, which has grown broad with the rising population.

「Probably for the same reason as you, Sensei.」

Ruful flopped her legs to the side in a girlish sit. Hopping down from her shoulder to her thigh so our eyes were about level, Tia said:

「I see. I should’ve said something, then. Have you been waiting long?」
「Not really… not that long.」

At my question she averted her gaze.

「Since morning—」
「Hey! Don’t blab that!」

Ruful answered with a sunny smile, and Tia threw both arms up and yelled.
I’ve learned over our long association that even among long‑lived races, the sense of time differs from person to person. The giant Ruful’s sense of time is as generous as her great body—sunrise to sunset isn’t much to her. By contrast, the pixie Tia’s feel for time is relatively close to a human’s.

「She should be here any minute.」
「What? You know where she is?」

Tia asked, dubious.

「Yeah. I let her carry one of my scales, so I’ve got a rough fix on her position.」
「Then we didn’t have to wait this long!」

Shouting that, Tia beat her wings and flitted back onto Ruful’s shoulder.

「Then next year, let’s ask Sensei and come together.」

To that, Ruful just smiled at her own pace.

「Look… here she comes.」

At my words, the two turned their eyes to the waterway running along the roadside.
It was the Hiiro Grand Canal Ruful had once built—a great ribbon of water that cut straight across the centaurs’ prairie from Hiiro Village to the Merfolk Bay.

「No, over there.」
「Wah!」

Before they could tilt their heads up, basari—big, pure‑white wings dropped over their faces.

「Mmph!? What!? What just happened!?」
「Ah—Rin‑chan, welcome back.」

Tia, buried almost to her whole body in feathers, panicked; Ruful offered a leisurely greeting.

「Ehehe. I’m home, Tia‑sensei, Ruful‑sensei. Surprised?」

Her blue hair gleaming in the sun, Rin shifted her arms from birds’ wings back into human arms,
and with a mischievous smile, hugged the two of them tight.

「Of course I was! What was that all of a sudden!?」
「You’re the one who let your guard down—」

Rin tittered. But I had seen it clearly: she’d dived in, hidden in backlight with the sun behind her, while the two looked out toward the waterway.
After parrying Tia’s near‑biting complaints, Rin abruptly hopped down from Ruful’s shoulder.

Look out!

Even with Ruful sitting on the ground, her shoulder was quite high. I hurried over to catch Rin, but she touched down first with a light ton.

Her legs had—at some point—become something catlike that absorbed impact with supple ease, and as she walked they slid back into human form. Even watching at point‑blank range, the change was so smooth I couldn’t tell when it happened.

「I’m home, Sensei.」

Landing right in front of me, Rin spoke with a soft, melty smile.

「…Welcome back, Rin.」

She really hasn’t changed, I found myself thinking.

「Honestly! Such a childish prank! You forgetful thing—don’t tell me you’ve forgotten me again!?」
「Yeah yeah, I remember you just fine, Tia‑sensei. And of course Ruful‑sensei too.」

Raising both hands in surrender to Tia as she whirled circles around us, Rin laughed.
Exactly fifty years ago now, Rin overcame age and death at the price of all her memories and returned to the form of an eight‑year‑old.
Which is why the girl before me is, so to speak, another Rin—a Rin walking a different life.

The phenomena where her memory lasted only a day, and where her past fell away, also stopped at that eight‑year‑old point. Even so, perhaps the forgetting left enough of a trauma that ever since then Tia has asked every time they meet whether Rin still remembers her.

「You’ve gotten awfully good at transformation magic. Did it stop requiring a price?」

Rin first managed to change her lower body into human legs at around a hundred fifty years old, so this is about ninety years earlier even by that measure. And back then, she shouldn’t have been able to speak while keeping human legs out.

「Oh, there is a price. In this form—」

Rin spread both arms, and as if by sleight of hand they became white birds’ wings.

「I can’t cook.」

Rin tightened her expression and declared it.

「Well, not with those arms.」
「Right. But with training I might manage to cook using my legs, and even if not I could at least ask someone and coordinate the prep, right? I can’t do any of that.」

I chuckled, and Rin eased back to a more natural look as she explained.

「Ah, a geis…!」
「Geis? What’s that?」

At my involuntary mutter, Rin cocked her head.

「A geis originally means a taboo—a vow that says, ‘I won’t do this.’ That line about not being able to cook didn’t happen on its own; you decided it yourself, right?」

Rin gave a surprised little nod.
A geis is a kind of pact with the gods found in Celtic myth: keep it and you gain strength; break it and ruin follows. The Irish hero Cú Chulainn’s ‘Don’t eat dog meat’ is a famous one.

In fact, equivalents to this can be found across many cultures. For example, in Japan there was a common vow of abstinence—giving up a favorite thing until the goal is achieved while praying for a good result—which is one such practice.

「This one is ‘swimming.’ So when I have human legs, I can’t swim—some mermaid I am.」

She slapped her long, slender legs with a smack and laughed, ahaha.

「So to use transformation magic, I have to get able to do lots of things—and each of those becomes the price.」

I see. So her magic only looks like it’s changing her body into something else; in reality, it’s converting skills she’s learned into physical capabilities.

「Then Rin’s cooking must be tasty enough to make you fly.」
「Yup. I’ve gotten a lot better this past year. I’ll treat you, Sensei and the others, so look forward to it.」
「Yaaay, I can’t wait!」

Rin took Tia’s teasing head‑on, and Ruful rejoiced innocently.
Should I call it strange, or only natural?
Rin had once again mastered transformation magic and taken to the road.

「But even in a year the village changes a lot. Mind if I take a quick lap?」
「No. Nina‑sensei’s exam first.」
「Okaaay.」

As Rin looked around restlessly, Tia nailed her down.
What’s different from before is that she now comes back to Hiiro once a year.
Not by her own choice—Nina imposed it.

「Nina‑sensei, we’ve brought her in—」
「Good work.」

At the clinic, Nina—now perfectly at home in her white coat—welcomed us.

「Outsiders are in the way. Out.」

So Tia and I were immediately kicked out. With nothing else to do, we linked up outside with Ruful, who couldn’t fit inside by sheer size.

「…Rin‑chan’s going to be okay, right?」
「It’ll be fine. It’s just a routine check.」

Ruful murmured anxiously, and Tia answered in a cool tone. But she was surely worried too—that’s why she’d waited to welcome Rin back.

Mermaids who live on land have markedly shorter lifespans than those who live in the sea.
In the past, Rin’s body began to fail at about half the age of her great‑grandmother Utai.

The direct cause is still unclear: perhaps fish scales get scraped and damaged against the ground, perhaps they simply dry out on land. Nina has guessed it’s something around there.
And she has also conjectured that those issues might be preventable if Rin keeps to human legs.

But it isn’t something you can see change in ten or twenty years. So Nina began giving Rin these regular annual checkups to monitor what effects were appearing—probably the oldest periodic health exam in the world.

「Huh? What are the three of you doing together?」

As we waited without so much as fidgeting for the exam to end, Yuuka happened by. With her red hair in a ponytail streaming and a stone sword at her hip, she made my heart give a tiny jolt.
Yuuka, a half‑elf born to Yutaka—the twenty‑fourth Head of the Sword Clan—and Light Blue, the elf exchange student.

Blood ties are distant; those long, taut ears and that slender, tall figure look nothing like her. And yet lately I often feel a hint of Yuuki in her—not, I think, merely because their names are similar.

「…Ah—did Rin‑chan come home?」
「Yep, she did.」

Ruful answered as Yuuka’s face lit up.

「So it’s today. Rin‑chan, welcome home!」

Before I could stop her, Yuuka threw the clinic door open.
Inside, Rin was being examined with her upper body bare.

…Ah.

I was glad to see her skin was smooth and beautiful, with no sign of decline or injury.

Thinking that, I resigned myself and took the water shot that came flying at me.