Most people think that ninjas are a thing of the past, but Rekka Hanabishi wishes otherwise. Although he comes from a family that makes fireworks, he likes to think of himself as a self-styled, modern-day ninja. Sounds like fun, right? Maybe not. Rekka ends up in lots of fights because he once made the bold announcement that if someone can defeat him, he will become their servant. Then one day, Rekka meets Yanagi Sak...