Aburidashi

Ninja technique
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Aburidashi is a ninja technique of sending secret messages using a form of invisible ink.[1] The technique uses ink made of juice extracted from soaked and crushed soybeans.[1] The message becomes visible to the recipient by heating the paper.

References

  1. ^ a b "Japan ninja student gets top marks for writing essay in invisible ink". BBC News. 10 October 2019. Retrieved 2019-10-10.


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