Ambush is when the player is getting attacked by an enemy. In many missions in Ninja Saga uses the ambush system in which the player would run through a forest, being "ambushed" five times a day and it is the same throughout the day. Players would even get ambushed at the end of a forest run.
Ambush System 2.0
In the 2.4.13880 version update, a new ambush system became available for Grade C Missions. In this ambush system, players would jump from tree to other trees, and some of the tree branches could have enemies lurking in them. Stepping on the wrong tree branch would cause an ambush. Unlike the ambush system 1.0, the amount of ambushes for the ambush system 2.0 does not stay constant and there may be only one or two battles.