To help you follow along with the Daniel Gate series.
Story starts at – http://ficlets.com/stories/12620

MAIN CHARACTERS
Daniel Gate – To his friends: a bike messenger. Our hero.

Nobutoshi Tohru – Daniel’s ‘client’. A man with a mysterious past and ties to the Yakuza.

Hideki Inagawa – Head of the Inagawa Kai

SUB -CHARACTERS
Nate: the cab-driver.
Lucas: Daniel’s as-yet-unseen friend.
Éponine and Cosette: two beautiful girls working for Nobutoshi.

MAFIA
Yakuza – The “Japanese Mafia”

Kokuryū-kai – A Yakuza family (gang). Nobutoshi owes them his loyalty. Also known as “The Black Dragon Society”, or simply “The Dragons”.

Inagawa kai – A Yakuza family. In a feud with the Kokuryū-kai.

The Yakuza and the families are real. You can read about them on wikipedia.com!