Dafu, whose full name is Katsuya Tabuse, stands as one of the foundational members of the Hikari Club. His history is deeply intertwined with the group's origins, as he was one of the trio of childhood friends, alongside Hiroshi Tamiya and Riku Kaneda, who first established their secret hideout in an abandoned factory during elementary school. This hideout would eventually evolve into the Hikari Club, a fact that marks Dafu as one of its original architects rather than a later recruit.

In terms of personality, Dafu is primarily characterized by his quiet and reserved nature. He is not among the more flamboyant or vocal members of the club, but he is recognized as being dedicated in his own way. Despite his typical silence, there is a notable and more disconcerting facet to his character. His personality is explicitly described with the label pervert, and he has a clear association with acts of self-gratification. This more base inclination provides a stark contrast to the club's lofty and aesthetic obsessions, revealing the primal and often ugly desires that lurk beneath their disciplined surface.

Dafu's motivations are largely defined by his intense personal loyalty. He is identified as being extremely loyal to Tamiya, his oldest friend. The initial spirit of the Hikari Club was one of shared camaraderie among Tamiya, Dafu, and Kaneda, and this bond continues to influence Dafu's actions even as the club transforms into something far more sinister. It is this loyalty that directly puts him in opposition to the club's new order. When the club, now under the authoritarian rule of Zera, kidnaps the girl Kanon and other female captives, Dafu aligns himself with Tamiya in an attempt to release the girls who are not Kanon. This act of defiance against Zera's absolute will demonstrates that Dafu's sense of morality, or at least his adherence to a prior code of friendship, has not been entirely extinguished by the group's decent into extremism.

This decision proves to be his pivotal role in the story's tragedy. Zera, having discovered the plot to release the captives, personally moves to eliminate dissent. Dafu, along with his friend Tamiya, becomes a target of Zera's brutal purge, resulting in his death at the leader's hands. His execution serves as a critical turning point, illustrating that within the club, loyalty is now owed only to the leader, Zera, and that the bonds of childhood friendship hold no power against the fascistic structure that has consumed the group. It is a moment of grim finality that cements the club's complete moral collapse.

Visually, Dafu is distinctive within the club's uniform aesthetic. While he wears the standard black gakuran school uniform and cap common to the members, he is also known for wearing an eyepatch, which has earned him the descriptor Dream Seeing Eyepatch. This eyepatch is a core part of his character design and is often listed among his key physical traits, alongside other notable features like his lipstick, distinguishing him from his peers. His design, like that of all the boys, adheres to the series' deliberate monochrome and gritty visual style. In terms of abilities, Dafu is not distinguished by any particular technical or strategic genius like some other members. His capabilities appear to be unremarkable compared to the likes of the club's scientist, Dentaku, or its chillingly efficient executioner, Jaibo. His narrative significance is derived not from a special skill, but from his role as a foundational member, a loyal friend, and ultimately, a tragic victim of the very institution he helped create. The prequel story, Bokura no Hikari Club, further explores the innocent origins of his friendship with Tamiya and Kaneda, humanizing him before the horrific events of the main narrative.