Sega's answer to Rolling Thunder in the company's never-ending arcade feud with Namco, the Shinobi series follows various members of the Oboro ninja clan through various struggles for Truth, Justice, and the Japanese Way.
This overall series is in turn broken up into about four major subseries: the main thread, that runs through (for better or worse) to Shinobi Legions; the Shadow Dancer thread; the GG Shinobi thread; and the PS2 series thread. You can follow the series evolution below.