[1] Seto was born in Los Angeles, California; he is Japanese-American Nisei, son of Issei parents.

Seto attended Arcadia High School, where he played numerous positions; he described himself as an "average player".

Concerned, Seto staged an "accidental" meeting with head coach John Robinson who sorted out his situation, allowing him to walk-on.

Once he had gained his bachelor's degree, Seto initially planned to attend graduate school at USC to become a physical therapist.

Although he had already placed his deposit, he found out about the possibility of a volunteer assistant position with the football program and opted to enter coaching.

[12] Seto married Sharla Marie (Chiang), who played soccer for USC and was on the Women of Troy's 1998 Pac-10 championship squad; and was originally from Seattle.

[13] He was featured in an episode of Trinity Broadcasting Network's "More Than Conquerors" magazine show, which profiles Christian sports figures and shares their testimony.

[14] Seto has participated in an exchange program with Waseda University in Tokyo, Japan to help teach American football coaching and playing strategy.