Hiyori Tomoe originates from the prestigious Tomoe Foundation, a family-centric conglomerate overseeing a national café chain that declined post-World War II yet maintains substantial influence. As the second son, he deliberately embraced a "foolish and playful" persona to shield his older brother, the family heir, while remaining fiercely dedicated to the family's honor. This self-sacrifice triggered a lasting identity crisis, leaving him feeling as though his heart had been "cut away and burned as fuel" to sustain his glittering façade, resulting in emotional hollowness and uncertainty about his authentic self. Initially attending Yumenosaki Private Academy, Hiyori served as a pivotal member of the unit *fine* with Nagisa and others. He departed after his contract lapsed, refusing to endorse Eichi Tenshouin’s dream-crushing methods of school reform. Outside the academy, he and Nagisa were scouted by Ibara Saegusa for COSMIC PRODUCTION. Hiyori then transferred to Reimei Academy as a third-year special student. There, he founded and led the unit *Eve*, partnering with Jun Sazanami—a former Reimei peer he "rescued from rotting in a garbage dump." Concurrently, he joined the overarching unit *Eden*, which houses the subunits *Adam* and *Eve* under COSMIC PRODUCTION. Hiyori’s personality fuses overt frivolity with concealed complexity. He projects a radiant, flamboyant, attention-seeking image, regularly declaring himself the "coolest and cutest idol globally." His noble birth fuels an open perception of others as socially inferior, and he acts on capricious whims, frequently causing disruptive delays that exasperate peers. Yet this masks an authentic nurturing instinct: he mentors others voluntarily, evidenced by his childhood guidance of Nagisa and steadfast support for Jun. He abhors being disliked and relentlessly pursues universal adoration, viewing idol work as a vehicle to "spread smiles and love worldwide." He evades painful discussions, particularly about family struggles or his conflicted *fine* history, though he still counts former *fine* members as friends. As an idol, Hiyori wields a crystalline, sweet singing voice and executes graceful, exquisite performances. Leading *Eve*, he prioritizes mesmerizing fans and engineering "the best day ever" for audiences. Post-graduation, he resides at Ensemble Square’s Seisoukan Apartments with roommates Rinne Amagi and Kanata Shinkai, continuing COSMIC PRODUCTION activities. He engages in the idol circle *Pretty 5*, asserting that "to be cute, one must know cute," and urges members like Tori Himemiya and Aira Shiratori to celebrate their uniqueness. Notable traits include conversational English fluency, revulsion toward insects and fish, exercise avoidance (deeming idol training adequate), and adoration for his merchandise. During his Reimei tenure, he adopted a stray dog named Bloody Mary, illicitly smuggling her into his dorm; she now lives with him at Ensemble Square, and he floods *Eden*’s group chat with her photos. He meticulously tracks fan trends, often adopting their whims—like consuming ice cream on chilly days—and treasures fan letters. Physically, Hiyori has wavy pale yellow-green hair, violet eyes, and delicately effeminate features. His style shifts seasonally, incorporating tailored elements like cream vests, plaid trousers, lavender coats, and accessories such as black watches or gold necklaces. He stands slightly tall with a "chubby figure, namely around the stomach area."