Devon Akina was an accomplice of Frank Delano and also Hillary Chaver's lover who appeared in the Season 2 finale episode, Ua Hala and the Season 3 premiere episode, La O Na Makuahine.
During those two episodes, Akina was seen conducting surveillance on the Five-0 Task Force led by Lieutenant Commander Steve McGarrett. He was also an accomplice and one of the murderers of Captain Vince Fryer.
Akina later kidnapped Officer Kono Kalakaua and Dr. Malia Waincroft, holding both women hostage. Akina later received a call from Delano telling him to dump Kono into the ocean which he did.
Despite Melia dying from her injuries much to Chin's devastation, Kono was eventually saved thanks to the efforts of her boyfriend, Adam Noshimuri.
In the Season 3 premiere episode, Akina was present when Delano helped Wo Fat escape from prison while he, Delano and three other men stole thirty million dollars worth of crystal meth but their getaway vehicle was intercepted after being caught in traffic due to a car accident, leading to an intense gunfight between the H50 team and Akina, Delano and the three unnamed men.
Akina attempted to flee but Kono responded by leaping onto the hood of his car before shooting him, presumably in revenge for Akina having her dumped in the ocean.
As a result, Akina died but not before revealing that Wo Fat had gone after Shelburne who was Steve's supposedly dead mother, Doris McGarrett.