A ninja (??) or shinobi (??) was a covert agent or mercenary in feudal Japan  who specialized in unorthodox warfare. The functions of the ninja included  espionage, sabotage

Covert Japan

Laboratory lessons in general science . Fig. 89. — Periods of revolution of  the planets (length of their years). ( ) The distance from sun to earth.  The time requiredfor light to

欅 坂 よね さん