In Shin Hakkenden, Cujo, also referred to as Kujo, is a significant supporting character who accompanies the protagonist, Kori. He is a unique being, described as a talking cyborg dog, blending organic canine traits with mechanical enhancements. His most distinctive physical feature is a special stone embedded in one of his teeth, which grants him a connection to the series' central mystical elements.

Cujo's primary role in the story is that of a faithful and valuable ally to Kori. He joins the young hero on his journey across the eight moons of the planet Heaven, offering both companionship and practical support. His calm and intelligent nature as a speaking cyborg provides a steadying influence, helping Kori overcome the numerous difficulties and dangers they face together. The bond between Cujo and Kori represents a key relationship, evolving into a deep and loyal friendship as they navigate a future where humanity has fled a dying Earth.

While the provided information does not detail a personal history or a significant character arc, Cujo’s motivations appear to be rooted in his loyalty to Kori and his role in the quest. His notable abilities include sapience, speech, and the power derived from the jewel in his tooth, which likely connects to the larger conflict involving powerful stones and the malevolent alliance of the Yuara, Ned, and Migi families. Beyond his relationship with Kori, the full extent of his connections with other characters like Nola or the guerrilla fighters is not elaborated upon. Fundamentally, Cujo serves as a steadfast companion, using his unique cybernetic and mystical capabilities to aid his friend in a struggle against forces threatening their new world.