Gentaro Yumeno, alias Phantom, is both a novelist and a member of the Shibuya rap crew Fling Posse. His layered pale brown hair and emerald green eyes accompany an outfit merging tradition with modernity: a white kosode layered over a black turtleneck, steel gray hakama held by a black obi tied with a yellow cord, a black capelet featuring purple lining secured by a chain and Fling Posse star pin, and black cap-toe boots. His Hypnosis Mic resembles a candlestick telephone, and his speakers manifest as red pedestal lanterns circled by flying omikuji paper fortunes.

He cultivates an elusive persona defined by constant deception, weaving truth and falsehoods seamlessly in speech and action. This extends to adopting varied vocal pitches and first-person pronouns during character roleplay. Outwardly snarky and quirky, he displays social awkwardness and prefers observing others over direct interaction. Beneath this facade lies loyalty to allies and a willingness to risk himself for their protection. He typically uses the archaic pronoun "shousei" outside of character roles. His rap ability, "Imitation," allows him to copy opponents' techniques in battle.

Gentaro's identity itself is a significant deception. He is the younger brother of the original Gentaro Yumeno, whose real name uses the characters 夢太郎 (pronunciation uncertain). After Chuohku authorities placed his brother into a coma for uncovering incriminating information, he assumed his brother's identity and career as a novelist. He continues this impersonation even after his brother awakens, driven by a desire to expose Chuohku’s injustices and avenge his sibling. His writing spans multiple genres, and he crafts stories inspired by Fling Posse members. He finds amusement in fabricating narratives about strangers, often concluding them with the phrase, "That was just a lie."

His Fling Posse collaborations include group tracks "Shibuya Marble Texture -PCCS-," "Stella," and "Trap of Fling," alongside division-wide albums "Division Rap Battle+" and "SUMMIT OF DIVISIONS." His solo works are "Scenario Liar" and "Calyx."

Key trivia notes his birthday on April Fools' Day, aligning with his deceptive nature. He prefers watermelon but dislikes melons. His quotes shift from Charlie Chaplin’s "What do you want meaning for? Life is desire, not meaning" to John Lennon’s "Being honest may not get you many friends but it’ll always get you the right ones." His name "Gentaro" combines characters meaning "phantom," "thick/big," and "son," while "Yumeno" means "dream field," references surrealist author Yumeno Kyusaku, and functions as a pun for "Gentaro of dreams."