Gentaro Yumeno is a novelist and member of Shibuya Division's rap group, Fling Posse. He cultivates an elusive persona, weaving truth and falsehood seamlessly through his words and actions, often adopting different voices and personas within his fabrications. His distinctive attire combines traditional Japanese elements: a white kosode layered over a black turtleneck, a patterned capelet, and a gray hakama secured by a black obi with a yellow cord. Comments on this clothing can cause him discomfort, making him withdraw or leaving him unable to respond defensively.

Born in a remote, snowy region, Gentaro was adopted by an elderly couple living a simple life. After the governing body Chuohku orchestrated a purge, his older brother—the original Gentaro Yumeno—fell into a coma. Seeking justice, Gentaro assumed his brother's identity. He maintained this deception even after his brother regained consciousness, continuing the name and public persona out of deep loyalty and a desire to expose Chuohku's injustices.

Gentaro's fabrications function as both a defense mechanism and a creative outlet. He frequently crafts intricate, observational stories about strangers, drawing inspiration from everyday encounters. When others believe his falsehoods, he often reveals the deception with phrases like "just kidding." His lying masks underlying kindness, helping him navigate social interactions while concealing insecurities and fear of rejection. He perceives himself as fundamentally disconnected from others, a trait echoing literary parallels with Dazai Osamu's *No Longer Human*, where a protagonist uses performative falsehoods to mask an inability to understand human nature.

Within Fling Posse, Gentaro exhibits fierce protectiveness towards teammates Ramuda Amemura and Dice Arisugawa. Despite habitual deception, he addresses Ramuda's concealed nature with candor, noting Ramuda's lack of "human" flaws and speculating about a dual personality. Gentaro prioritizes the group's safety and objectives, even after being initially coerced into joining. His rap ability, "Imitation," allows him to replicate opponents' techniques during battles, aligning with his themes of identity and adaptation.

Gentaro's personal history and motivations drive his actions, with his quest to challenge Chuohku forming a consistent narrative thread. His character explores themes of authenticity, loyalty, and the psychological burden of sustained deception.