Japan ninja student gets top marks for writing essay in invisible ink www.bbc.co.uk

Image caption Eimi Haga became interested in ninjas by watching TV showsA 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.
Eimi Haga followed the ninja technique of "aburidashi", spending hours soaking and crushing soybeans to make the ink.
The words appeared when her professor heated the paper over his gas stove.
But, to ensure her professor didn't put the essay in the bin, she left a note in normal ink saying "heat the paper".
"I was confident that the professor would at least recognise my efforts to make a creative essay," she said.