Jim Cusack is a marine biologist entrusted with the care and supervision of Umi and Sora, two boys raised by dugongs who possess unique aquatic abilities. His professional background places him in direct opposition to Anglade, another marine biologist and former friend, stemming from their conflicting scientific philosophies and methodologies. While Anglade pursues the mystery surrounding the boys with potentially exploitative intentions, Jim adopts a protective stance, prioritizing their well-being and autonomy.

His approach reflects a broader philosophical perspective that emphasizes the potential for extraordinary phenomena to shift human understanding and perception of the world. He champions the idea that witnessing the unexplained could fundamentally alter how individuals perceive reality and their place within the natural order. Jim partners with Dede, a mysterious figure who also watches over Umi and Sora, indicating their shared role in safeguarding the brothers.