Miller hails from Miracle Island, the setting of a single film, which he calls home and where the story unfolds. He possesses special powers intrinsically linked to the island's unique rainbow carnation, a flower believed to grant wishes when given to someone special. This carnation defines Miller and his connection to the island.

His prized flower is stolen by an evil magician, sparking the central conflict. Devastated by the theft, Miller sets out on a journey. He joins forces with Shimajirō and others to reclaim all the stolen rainbow carnations from the magician's grasp. Their quest is driven by the theme of gratitude, where saying "thank you" acts as a magical phrase to remember loved ones, reflecting the carnation's profound significance.