A Japanese student of ninja history who handed in a blank paper was given top marks - after her professor realised the essay was written in invisible ink.

日本一名研究忍者歷史的學生論文交了“白卷”，卻得到了最高分，因為教授發現這篇文章是用隱形墨水寫的。

Eimi Haga followed the ninja technique of "aburidashi", spending hours soaking and crushing soybeans to make the ink.

羽賀英美采用了一種忍者“烤墨紙”技術，她花費數小時浸泡、研磨豆子來制作墨水。

The words appeared when her professor heated the paper over his gas stove.

教授把她的論文放到煤氣爐上方加熱后，論文就顯示了出來。

"It is something I learned through a book when I was little," Ms Haga told the BBC. "I just hoped that no-one would come up with the same idea."

羽賀英美告訴英國廣播公司說：“這是我小時候從一本書中學到的。我只是希望自己的想法獨一無二。”

Ms Haga has been interested in ninjas - covert agents and assassins in medieval Japan - since watching an animated TV show as a child.

在小時候看過一部動畫片后，羽賀英美一直對忍者（中世紀日本的秘密特工和刺客）很感興趣。

After enrolling at Mie University in Japan, the first-year student took a class in ninja history, and was asked to write about a visit to the Ninja Museum of Igaryu.

入讀日本三重大學后，這位大一新生選了一門關于忍者歷史的課，教授要求學生們寫一篇參觀伊賀市忍者博物館的文章。

"When the professor said in class that he would give a high mark for creativity, I decided that I would make my essay stand out from others," she said.

她說：“教授在課堂上富有創造力的文章會打高分，我決定讓我的文章脫穎而出。”

"I gave a thought for a while, and hit upon the idea of aburidashi."

“我想了一段時間，突然想到了‘烤墨紙’這個主意。”

Ms Haga, 19, soaked soybeans overnight, then crushed them before squeezing them in a cloth.

19歲的羽賀英美將大豆浸泡一夜，然后將其碾碎，再用布將其擠壓。

She then mixed the soybean extract with water - spending two hours to get the concentration right - before writing her essay with a fine brush on "washi" (thin Japanese paper).

然后，她把大豆提取物加水攪拌，花了兩個小時讓濃度適宜，然后用細毛筆在“和紙”（日本的薄紙）上寫了論文。

Once her words had dried, they became invisible. But, to ensure her professor didn't put the essay in the bin, she left a note in normal ink saying "heat the paper".

筆跡干了之后，上面的文字就會消失。但是，為了確保教授不會把論文當成垃圾扔掉，她用普通墨水寫了一張紙條，上面寫著“把紙加熱看看”。

The professor, Yuji Yamada, told the BBC he was "surprised" when he saw the essay.

教授山田裕二告訴英國廣播公司說，他看到這篇論文時感到“很驚訝”。

"I had seen such reports written in code, but never seen one done in aburidashi," he said.

他說：“我見過用代碼寫的論文，但從未見過用‘烤墨紙’寫的。”

"To tell the truth, I had a little doubt that the words would come out clearly. But when I actually heated the paper over the gas stove in my house, the words appeared very clearly and I thought 'Well done!'

“說實話，我有點懷疑這些文字是否能清楚地顯示出來。但當我在家里的煤氣爐上加熱這張紙時，上面的字看得很清楚，我心里想，‘干得漂亮’!”

"I didn't hesitate to give the report full marks - even though I didn't read it to the very end because I thought I should leave some part of the paper unheated, in case the media would somehow find this and take a picture."

“我毫不猶豫地給這篇論文打了滿分——盡管我沒有把它讀到最后，因為我覺得我應該留出一部分未加熱的紙張，萬一有媒體知道這件事想拍照呢。”

As for the essay itself, Ms Haga said it had more style than substance.

至于這篇論文本身，羽賀英美表示，其形式大于內容。

"I was confident that the professor would at least recognise my efforts to make a creative essay," she said.

她說：“我相信教授至少會認可我為寫一篇有創意的論文所付出的努力。”

"So I wasn't really worried about getting a bad score for my essay - though the content itself was nothing special."

“所以我并不怎么擔心論文會得低分，盡管內容本身很普通。”

A Japanese student of ninja history who handed in a blank paper was given top marks - after her professor realised the essay was written in invisible ink.

日本一名研究忍者歷史的學生論文交了“白卷”，卻得到了最高分，因為教授發現這篇文章是用隱形墨水寫的。

Eimi Haga followed the ninja technique of "aburidashi", spending hours soaking and crushing soybeans to make the ink.

羽賀英美采用了一種忍者“烤墨紙”技術，她花費數小時浸泡、研磨豆子來制作墨水。

The words appeared when her professor heated the paper over his gas stove.

教授把她的論文放到煤氣爐上方加熱后，論文就顯示了出來。

"It is something I learned through a book when I was little," Ms Haga told the BBC. "I just hoped that no-one would come up with the same idea."

羽賀英美告訴英國廣播公司說：“這是我小時候從一本書中學到的。我只是希望自己的想法獨一無二。”

Ms Haga has been interested in ninjas - covert agents and assassins in medieval Japan - since watching an animated TV show as a child.

在小時候看過一部動畫片后，羽賀英美一直對忍者（中世紀日本的秘密特工和刺客）很感興趣。

After enrolling at Mie University in Japan, the first-year student took a class in ninja history, and was asked to write about a visit to the Ninja Museum of Igaryu.

入讀日本三重大學后，這位大一新生選了一門關于忍者歷史的課，教授要求學生們寫一篇參觀伊賀市忍者博物館的文章。

"When the professor said in class that he would give a high mark for creativity, I decided that I would make my essay stand out from others," she said.

她說：“教授在課堂上富有創造力的文章會打高分，我決定讓我的文章脫穎而出。”

"I gave a thought for a while, and hit upon the idea of aburidashi."

“我想了一段時間，突然想到了‘烤墨紙’這個主意。”

Ms Haga, 19, soaked soybeans overnight, then crushed them before squeezing them in a cloth.

19歲的羽賀英美將大豆浸泡一夜，然后將其碾碎，再用布將其擠壓。

She then mixed the soybean extract with water - spending two hours to get the concentration right - before writing her essay with a fine brush on "washi" (thin Japanese paper).

然后，她把大豆提取物加水攪拌，花了兩個小時讓濃度適宜，然后用細毛筆在“和紙”（日本的薄紙）上寫了論文。

Once her words had dried, they became invisible. But, to ensure her professor didn't put the essay in the bin, she left a note in normal ink saying "heat the paper".

筆跡干了之后，上面的文字就會消失。但是，為了確保教授不會把論文當成垃圾扔掉，她用普通墨水寫了一張紙條，上面寫著“把紙加熱看看”。

The professor, Yuji Yamada, told the BBC he was "surprised" when he saw the essay.

教授山田裕二告訴英國廣播公司說，他看到這篇論文時感到“很驚訝”。

"I had seen such reports written in code, but never seen one done in aburidashi," he said.

他說：“我見過用代碼寫的論文，但從未見過用‘烤墨紙’寫的。”

"To tell the truth, I had a little doubt that the words would come out clearly. But when I actually heated the paper over the gas stove in my house, the words appeared very clearly and I thought 'Well done!'

“說實話，我有點懷疑這些文字是否能清楚地顯示出來。但當我在家里的煤氣爐上加熱這張紙時，上面的字看得很清楚，我心里想，‘干得漂亮’!”

"I didn't hesitate to give the report full marks - even though I didn't read it to the very end because I thought I should leave some part of the paper unheated, in case the media would somehow find this and take a picture."

“我毫不猶豫地給這篇論文打了滿分——盡管我沒有把它讀到最后，因為我覺得我應該留出一部分未加熱的紙張，萬一有媒體知道這件事想拍照呢。”

As for the essay itself, Ms Haga said it had more style than substance.

至于這篇論文本身，羽賀英美表示，其形式大于內容。

"I was confident that the professor would at least recognise my efforts to make a creative essay," she said.

她說：“我相信教授至少會認可我為寫一篇有創意的論文所付出的努力。”

"So I wasn't really worried about getting a bad score for my essay - though the content itself was nothing special."

“所以我并不怎么擔心論文會得低分，盡管內容本身很普通。”