A Japanese student got top marks for an essay was written in invisible ink.
Eima Haga – first-year student at Mie University in Tsu, Mie, Japan – had to write about the Ninja Museum of Igaryu for a ninja history class, with the promise of high marks for creativity.
According to the BBC, the 19-year-old woman decided to use the ninja technique of “aburidashi” by soaking and crushing soybeans to make the ink.
The words written using this can then be read when the paper is heated over a stop.
Haga said: “It’s just something I learned through a book when I was little.”
The professor, Yuji Yamada, told the BBC he was “surprised” when he saw the essay.
“I had seen such reports written in code, but never seen one done in aburidashi,” he 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!’
“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.”