Deep underneath Tokyo there is an old, abandoned city once used by drug lords and the homeless. Now, it has been claimed by the Kobayashi clan and is used as a base of operations for their villanous actions.
It still houses the more unfortunate souls of Tokyo. Drug dealers, addictees, homeless, criminals, etc.
The city has quite a few openings to it, all guarded by heavy steel doors and security cameras. Only those with the pass code to the various doors will be able to enter. 1 pass code per door.