Ryoji Mochizuki is a pivotal character in Persona 3, serving as a mysterious transfer student who quickly becomes popular due to his friendly and charming demeanor. As the story progresses, Ryoji is revealed to be the human manifestation of Death, also known as the Appriser or the 'Nyx Avatar'. His existence is closely tied to the game's main plot and the fate of the protagonist and SEES, making him central to the narrative's climax and resolution.