Love Shockers gang 
Successfully complete all Shibuya-cho levels with a "Jet" rank to unlock the Love Shockers gang.

Noise Tank gang 
Successfully complete all Benten-cho levels with a "Jet" rank to unlock the Noise Tank gang.

Poison Jam gang 
Successfully complete all Kogane-cho levels with a "Jet" rank to unlock the Poison Jam gang.

Goji Rokkaku 
Unlock the Love Shockers, Noise Tank, and Poison Jam gangs, then successfully complete all the Grind City levels with a "Jet" rank to unlock Goji Rokkaku.

Pots (the Dog) 
First, unlock all the bonus characters (Love Shockers, Noise Tank, Poison Jam, and Goji). After completing the game, play the "Monster of Kogane" level before "Benten Boogie". After completing those levels, a Noise Tank will challenge you after Chapter 2. Defeat the Noise Tank Challenge to unlock Pots.

Skate backward 
While skating, press Down, Up.