Rules card says:
At the start of each planning phase, the ninja player may choose to use their Spy Token by placing it on any Village Area on the board. The ronin player must then divulge any and all ronin that will be assigned to that area this round.
If the ninja player cannot or does not want to use their Spy Token, the ronin player may use their spy token by placing it on any Village Area on the board. The ninja player must then divulge how many ninja (if any) will be assigned to that area this round.
Each token may only be used once per game.