Kenshi Sentai Ninjaman

Kenshi Sentai Ninjaman (Swordsman Squadron Ninja Man) is a Super Sentai fanfiction created by Sonic Flash. It has an american Power Rangers counterpart Power Rangers Ninja Quest.

Plot
Pirates from the underworld escape because of the nature and technology imbalance and try to conquer the earth and claim it as their own. To stop them, a secret ninja academy trains five ninja students to become a new team of heroes: the Kenshi Sentai Ninjaman.