"He is stronger than steel
and moves faster than a whirlwind.

Sometimes he hides in mud.
Other times he transforms his
shape like an ever changing cloud.

Although his fighting spirit burns
like fire, his mind is as calm as
still water.

Should Shinobi fail before
completing the mission, he will
disappear before the dawn and
vanish forever.

Keep this knowledge in your heart
and mind."

--From the
'Secret Manual of Oboro Ninjitsu'

https://www.gamefaqs.com/genesis/586455-shinobi-iii-return-of-the-ninja-master/faqs/30569