Agena, of Japanese descent, was born in Honolulu, and began acting at the age of 10. She attended Mid-Pacific Institute preparatory school in Oʻahu, and Whitman College for one year as a drama major.
Agena married Shin Kawasaki in a helicopter over Las Vegas Valley, Nevada, on December 19, 2005.
Agena rides motorcycles, she arrives at the Warner Brothers studio lot on a Yellow 1970s Kawasaki Ninja 250.