Get to play as Goji Rokkaku:
     To  play  as  Goji,  you  first have to unlock the three previous
gangs  (Poison Jam, Love Shockers, and Noise Tank), and then get a jet
ranking on the Grind City stages.

Get to play as Love Shockers:
     To  play  as  these  guys  you have to complete every Shibuya-cho
stage with a jet rating.

Get to play as Noise Tank:
     To play as the toxic gang, complete every Benten-cho stage with a
jet rating.

Get to play as Poison Jam:
     You  can play as the gang members with the funny monster costumes
by getting a jet ranking on ever Kogane-cho Story stage.

Get to play as Potts the Dog:
     To get to play as Jet Grind's dog, you first have to complete the
game  and  have  all  of the previous characters (Goji, Love Shockers,
Noise  Tank,  and  Poison Jam) unlocked. Next you have to play through
the  game  again  and complete Monster of Kogane before Benten Boogie.
After  Chapter 2, Noise Tank will challenge you. Win that challenge to
get to play as Potts.

Secret Items:
     First, complete the entire game from beginning to end, Then after
the credits, save the defeated game onto your VMU. Restart the system,
and  then  go  play  the  following  in  succession. System Crush, Jet
Technique  and  Jet Grafitti in the Tokyo levels and Benton street. On
Jet technique, do a X10 Combo vs. your opponent and you should recieve
boost  jets, extra spray cans, faster skates and much more. Keep doing
the combo to get more and more of what was just described.