Joe is described in the series guidelines as a "tragic, troubled loner" who has been defined by his past experiences with Gallactor. He seeks revenge against this organization for killing his parents when he was eight years old. His father, Giuseppe Asakura, was once a high-level leader in Gallactor but ran afoul of organizational politics or developed a conscience and sought asylum with the ISO. Joe's motives are unclear, but he was waiting to meet with Dr. Nambu when he was fatally shot by a Devil Star along with his wife. Joe nearly died himself but was rescued by Dr. Nambu and later trained for the Kagaku Ninjatai. He had no clear memories of his parents' deaths or Gallactor's motives for their assassination until later on.
Joe acts as a counterbalance to Ken, being impulsive, impatient, and furious when Ken is lucid but stable and sensible when Ken is acting irresponsibly. He is an expert marksman who serves as the chief gunner of the team. His preferred mode of action is "Shoot it now and improvise the rest," but he is not a cold-blooded murderer. Joe excels at hot-wiring his way out of tricky situations and throwing darts and knives, which has become his trademark weapon.