Jim Cusack is a researcher at an aquarium dedicated to studying unusual marine phenomena and the alarming disappearance of fish populations. He maintains a strictly professional relationship with his colleague Azumi, who is also his former brother-in-law, at the same facility. His work involves meticulous monitoring of marine life patterns and investigating global oceanic disturbances.

He relies on an assistant for documenting and analyzing these marine anomalies, though the assistant's specific background is not defined. Cusack's scientific research directly intersects with the aquarium's study of two mysterious boys, Umi and Sora, who display unique connections to oceanic environments. He facilitates their observation and research within the aquarium's controlled setting.

His approach embodies a scientific perspective on unexplained natural events, contrasting sharply with the more spiritually inclined interpretations of others. He expresses deep curiosity about how extraordinary phenomena might alter human perception, suggesting exposure to the unknown could fundamentally shift understanding of reality. A subplot involves his interactions with military or governmental entities showing interest in the marine disturbances, though the precise nature of this involvement remains undefined.

His background story outside his professional role at the aquarium is not elaborated upon. Primarily, his character serves to bridge scientific inquiry with the narrative's exploration of cosmic and oceanic interconnectedness, particularly by facilitating access to the aquarium's resources for investigating the central marine mysteries.