Tetsu is a school friend of Ryuunosuke Oohara and Naoki Satoya. He becomes inadvertently entangled in the central conflict after sharing information about Ryuunosuke's potential succession as the next leader of the Oohara yakuza family. Excited by this prospect, Tetsu enthusiastically informs third-year students of the impending leadership shift, unaware of the repercussions. His actions lead rival gang members to target Ryuunosuke, resulting in violent confrontations. Tetsu initially fails to grasp the severity of his role or the reason for Ryuunosuke and Naoki's negative reactions. He displays confusion when confronted about escalating the situation, directly questioning what he did wrong after witnessing their responses. Tetsu's background, motivations, and any development beyond this incident are not detailed, as his role remains confined to this specific event.