She's high-kicking. She's power-punching. She's back-flipping. Quick as a cat. Silent as a shadow. She's over 70? When twelve-year-old twins Josh and Jessica visit their old gran in Tokyo things aren't quite what they expected, for starters her flat is the most high-tech place they've ever been outside Dixon's. Suffice to say it makes them a little suspicious. But when their friend, popstar Kiki, is kidnapped and the twins set out to investigate they find themselves aided by a mysterious hooded ninja. But who is this shadowy crimefighter? None other than their gran! She's been busting crime for as long as she can remember as Tokyo's secret ninja agent. But can the twins and their granny piece together the kidnap mystery and rescue Kiki in time? The first in the high-kicking martial arts adventure series filled with crimefighting action!