Izumi is the third boss of The Four Kings that you face in the Story. Defeating her grants you access to the next Area. It's revealed that the presumed "Emperor" (The Joker) was sending threatening letters to her group, so her gang despised The Emperor. After defeating her, she befriends Namiko and your character and later on in the Story helps your character to take down The Emperor.
Izumi's normal avatar is awarded upon defeating her.
She drives a Innocent Blue Mica Mazda RX-7 FD3S