Five Element Ninjas (1982)

A young martial artist seeks revenge on the Ninja who kills his martial arts brothers and teacher. He finds help in the form of a new teacher (who knows Ninjitsu) and new brothers. Together the four pupils face the Five Element Ninja challenge: Wood, Earth, Gold, Water, and Fire.

When the leader of a clan of elite Chinese warriors receives an invitation to a battle at five locations from the five elements ninjas he suspects a trap. Rightly so - when he caught one of the ninja's rings thrown to him by a disembowelled samurai he was poisoned and he knows he is now unable to use his kung-fu for 'about three months'. So, he considers the offer carefully but eventually decides to follow the elaborate instructions on the invitation to the letter. 90% of his best warriors are predictably ambushed and wiped out, including one being slain by the perverted 'earth' ninjas. What will happen next? Who cares. It will be funny.