Rinfu reigns as King in New Kyoto, commanding significant authority. His deep history with childhood friend Teruto Kurabe is pivotal; Rinfu orchestrated Teruto's entry into this world and the resulting loss of Teruto's memories. Initially appearing as a detached observer, Rinfu manipulates events from the shadows, specifically guiding Teruto to challenge other Kings through the Build Divide card game.

A formidable Build Divide player, Rinfu employs a deck themed after "The Tale of the Bamboo Cutter." His interactions with Kuon and Hikaru reveal complex dynamics. Rinfu's connection to Teruto's forgotten past and the circumstances of the memory loss fuels his actions, indicating a personal stake in New Kyoto's fate. While often projecting a calm and enigmatic demeanor, moments of conflict, particularly with Teruto as memories resurface, expose deeper emotions and potentially conflicting loyalties.

Rinfu's ultimate goals remain mysterious for much of the narrative. He navigates the intricate power struggles between the Kings, leverages Teruto's growth, and confronts the consequences of past choices. This culminates in a direct, high-stakes Build Divide confrontation with Teruto, where their shared history and opposing viewpoints clash. The outcome of this battle and revelations about their past mark a significant turning point. Rinfu's fate intertwines with the larger conflict surrounding New Kyoto's structure and the entity known as the World. His actions directly impact the world's future and the resolution of the central storyline involving the Kings and their system.