It was previously confirmed that the actor will play a coroner in the fourth episode of the cop drama.
"I'm playing an odd little man named Max Bergman," he told TV Guide. "He's brilliant at two things - being the Honolulu medical examiner and playing the piano, which he does in his autopsy room office to help him think."
Oka also revealed details of what Heroes creator Tim Kring had planned for a fifth season of the axed NBC series.
"They were going to end everyone's stories by bumping off one character every week," he confirmed.
Oka's appearance on Hawaii Five-0 is expected to air in October. His character could potentially recur throughout the first season.