Popo appears in the anime Kaiba as its main antagonist. He is a teenage boy with medium brown eyes and brown hair, which he wears in a distinctive long front pompadour style. As a child, Popo was recruited along with a large group of orphans by the organization Issoudan, an anti-memory chip organization. During this time he befriended two other orphans, Neiro and Cheki, and made a childhood promise to become a king so the three of them could live happily together, with Cheki able to eat nippos every day. This promise is the driving force behind his ambitions.

In the present, Popo serves as the more public voice of Issoudan, an organization that opposes memory chip technology and is dedicated to destroying Warp for the wrongs he allegedly committed and ridding the world of what it considers evil technologies. Popo is a powerful public speaker, and his confidence and determination to realize Issoudan's goals allow him to continually rise in the organization's ranks. His outward commitment to the cause, however, masks a more personal motivation: he wishes to take power for himself.

Popo is the first person to encounter Kaiba after Kaiba awakens with no memories. When they cross paths again, Popo explains the nature of the world to Kaiba and warns him that his life is in danger. He gives Kaiba the temporary name Warp, smuggles him onto the freight ship Neuron, and creates a diversion so Kaiba can escape from Cloak, a man pursuing Kaiba's special body. Despite this early assistance, Popo is secretly an adversary; Issoudan is destined to destroy Warp, and Popo's help is part of a larger scheme.

Popo is fiercely loyal to his childhood friends Neiro and Cheki, but his devotion to Issoudan often proves stronger, and he is shown harming others for the cause, even his own companions. Before the events of the series, he has Neiro's memories modified so that all of her good memories involve him and all of her bad memories involve Warp, ensuring her loyalty. This act illustrates how far he is willing to go to secure the people and power he wants. Popo's development in the story follows his gradual abandonment of his ideals in favor of self-serving ambition, even as the childhood promise that started him on this path continues to define him. His notable abilities are primarily social and rhetorical; his charisma and skill as a public speaker are what allow him to advance within Issoudan and to sway others to his cause.