Imperador Gross instigates the central conflict by abducting Haruhiko Shiki, Kakeru's father. He fears Haruhiko's unpublished news story could expose regime weaknesses and trigger his overthrow. This kidnapping directly propels Kakeru's quest to rescue his father across territories under Gross's dominion.

His authority spans multiple locations. The Yellow Fortress imprisons citizens and captives like Haruhiko. Imperial forces enforce his will in places such as Brown Town, coercing townspeople to build castles and trains as gifts for his niece. His strategic control extends to the dark ship, transporting prisoners like Haruhiko along the dark river.

Gross maintains psychological control through manipulation and intimidation. He silences fortune-tellers in Mint Green, preventing them from revealing Haruhiko's location to Kakeru. His governance indirectly fuels decay, reducing once-prosperous Yellow Town to ruins. His oppressive systems benefit his niece, who receives territories like Brown Town as gifts.

His ultimate fate remains unresolved within the series narrative. Despite Kakeru's persistent efforts to find his father and confront the emperor, Gross himself never appears directly in the documented episodes. His role persists as an overarching threat driving the protagonists' journey through lands scarred by his reign.