Yeah, with older books like this it wouldn’t be surprised if an official translation (or even several!) are already in the training dataset.
I have access to GPT-4, so I did a test with a book translated in 2022. Should be recent enough to not be part of the training. It’s the beginning of the short story 素敵な素材 in the book 生命式 by Sayaka Murata
prompt
The following Japanese text is the opening passage of the novel 生命式 by Sayaka Murata. Translate this passage into natural and smooth modern English.
休日の午後、私は大学時代からの女友達二人と、ホテルのラウンジでお茶をしながらお喋りを楽しんでいた。窓の外は晴天で、オフィス街の灰色のビルが並んでいる。予約が大変だったというホテルのラウンジは、私たちと同じようにアフタヌーンティーを楽しむ女性客でにぎわっていた。白髪の上品な女性が、深い紫色のストールを羽織り、優雅にタルトを口に運んでいる。私たちの隣のテーブルでは、色とりどりのネイルを塗った女の子たちが、ケーキの写真を撮っている。そのうち一人が、白いカーディガンにアプリコットのジャムを溢してしまい、慌ててピンクのハンカチで拭っている。
メニューを開いて紅茶のおかわりを注文し終えたユミが、ふと、私の着ているセーターに目を止めた。
「ねえナナ、そのセーター、人毛？」 私は顔を綻ばせて頷いた。
「あ、わかる？ そうそう、100％」 「いいなあ、高かったでしょ」
「うーん、 少しね……。 ローン組んじゃった。 でも、こういうものって、一生ものだから」
私はちょっと照れながらそう答え、自分が着ている真っ黒なセーターを指先でそっと撫でた。三つ編みが並んでいるようなデザインのセーターは、手首と裾に複雑な編み込みで模様が施されており、きっちりと編まれた黒髪が艶めいて、窓からラウンジに差し込む光を反射して光っている。 自分で着ていてもうっとりと眺めてしまうほど美しい。
アヤも羨ましそうにセーターを見て言った。
「やっぱり、冬は人毛100％が最高だよね。暖かいし、丈夫だし、高級感もあるし。私のセーターにも人毛入ってるけど、高いからウール混合のやつしか買えなかったんだ。やっぱり手触りが違うね、100％は」
「ありがとう。勿体なくていつもは仕舞い込んでるんだけど、今日はホテルだし、久しぶりに二人に会えるし、お洒落しようと思って、思い切って着てきちゃった」
「えー、 せっかく買ったのに、沢山着ないと勿体ないよー！」
GPT-4 translation
On a holiday afternoon, I was enjoying chatting over tea with two female friends from my college days at a hotel lounge. Outside the window, the weather was clear, and rows of gray office buildings lined the streets. The hotel lounge, which was said to be difficult to book, was bustling with women customers enjoying afternoon tea just like us. An elegant white-haired lady was wearing a deep purple shawl and gracefully lifting a tart to her mouth. At the table next to ours, girls with colorful nails were taking pictures of their cakes. One of them accidentally spilled apricot jam on her white cardigan and hurriedly wiped it with a pink handkerchief.
Having finished ordering a refill of her tea from the menu, Yumi suddenly fixed her eyes on the sweater I was wearing.
“Hey Nana, is that sweater made of human hair?” I grinned and nodded in agreement.
“Ah, you know? Yes, that’s right, 100%.”
“It must have been expensive, right?”
“Well, a little… I had to take out a loan. But, you know, something like this is a lifetime treasure.”
Feeling slightly embarrassed, I answered and gently stroked the pitch-black sweater I was wearing with my fingertips. The sweater, with a design resembling rows of braids, featured intricate patterns on the cuffs and hem, and the neatly woven black hair gleamed, reflecting the light streaming into the lounge from the window. It was so beautiful that I couldn’t help but admire it even while wearing it.
Aya also looked enviously at the sweater and said,
“Human hair is really the best for winter, isn’t it? It’s warm, durable, and has a luxurious feel. My sweater has some human hair in it, but because it’s expensive, I could only afford one with a wool blend. The 100% definitely feels different.”
“Thank you. I usually keep it tucked away because it feels too precious, but today, since we’re at a hotel and I’m meeting you two after such a long time, I thought I’d dress up and decided to wear it.”
“What? You should wear it more often since you bought it! It’s such a waste not to!”
official translation
A First-Rate Material
It was a holiday, and I was enjoying chatting with two girlfriends from
university days over afternoon tea. Through the window, the gray office
buildings of the business district sat beneath a cloudless sky. Reser-
vations at this hotel lobby tearoom were hard to come by, and it was
thronged with a female clientele. An elegant white-haired lady with a
deep purple stole across her shoulders daintily carried a piece of tart to
her mouth. At the table next to us, some girls with colorful painted nails
were taking photos of their cakes. One of them spilled apricot jam on
her white cardigan and hastily started wiping it off with a pink handker-
chief.
Yumi opened the menu and ordered a second cup of tea, then no-
ticed the sweater I was wearing.
“Hey, Nana, that sweater . . . is it human hair?”
“Oh, can you tell?” I beamed at her, nodding. “Yes, one hundred
percent.”
“Fantastic! It must have been expensive.”
“Yeah, a bit . . . I took out a loan. But it’ll last me for life,” I answered
rather bashfully, lightly running my fingertips over the garment. The jet-
black hair was closely knitted into rows of braids, with an intricate weave
at the cuffs and neck, and it glistened alluringly in the rays of light shin-
ing in through the lobby windows. Even though it was mine, it was so
beautiful, and I gazed at it, enraptured.
Aya was eyeing it enviously too. “A hundred percent human hair is
just the thing for winter! Warm, durable, and luxurious. My sweater con-
tains some too, but it’s so expensive I could only afford it mixed with
wool. But human hair really does feel completely different, doesn’t it?”
“Thanks. It’s too special to wear every day, and normally I keep it
safely stored away, but today I really wanted to dress up—it’s the first
time we’ve seen each other for ages, and coming to a hotel, too.”
“Really? But now that you’ve bought it, it’s such a waste not to wear
it more,” Yumi said.
! Funnily enough, I don’t actually remember it being repeated that often in Minna no Nihongo, so I was a bit surprised to find out it was apparently a bit of a meme. I was grateful to learn it, though, because it was one of the first lines from a pro wrestling promo that I was able to understand on my own without needing a translation!
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