He is the first shown victim of The Phantom Arsonist found as a burned corpse inside his vehicle on a public street.
Arson Investigator Phil Bosso suggests his death was by self-incineration (a form of Suicide). Dexter however notices an inconsistency in this where the backseat of the car is void of scorch marks from the flames, suggesting there was something there (which is later pointed out at the crime scene for Leo Santolongo).
According to his ID badge which was found in his car, Yamiro was a paralegal that worked downtown. The reason the Phantom chose him is unknown.