Ninja History Student Gets ‘A+’ For Using Homemade Invisible Ink on Test

Eimi Haga, a first-year student who took up ninja history class at Mie University in Japan, was asked to write an essay during her visit to the Ninja Museum of Igaryu, according to BBC.

“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,” the 19-year-old student told the publication. “I gave a thought for a while, and hit upon the idea of aburidashi.”

Aburidashi is an ancient method for ninjas to communicate using invisible ink dating back to the Edo Period between 1603 and 1867. The ink, made with crushed soybeans extract, or sometimes even rice-wine, alum, or citrus juice, becomes invisible when dried up and can only be seen when it is heated, Huffington Post reported.

Haga has been interested in ninjas ever since she was a child after watching animated television shows featuring the covert agents and assassins in medieval Japan.

“It is something I learned through a book when I was little,” she said. “I just hoped that no-one would come up with the same idea.”

Haga spent two hours just to get the concentration right when she mixed the soybean extract with water. With much success, she was able to turn the ink invisible, but in order to ensure that her professor, Yuji Yamada, wouldn’t throw away her work, Haga included a note with a regular ink saying, “heat the paper.”

The student already prepared herself for a possible bad score, but said she was confident her professor would “at least recognize my efforts to make a creative essay.”

“So I wasn’t really worried about getting a bad score for my essay – though the content itself was nothing special,” she continued.

However, Haga didn’t expect that her professor would be surprised and like her work.

“I had seen such reports written in code, but never seen one done in aburidashi,” professor Yamada said. “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!’”

Yamada was so pleased with her work that it was no question to give her a top score.

“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,” he said.