Yū Saegusa, a 16-year-old actress and esports prodigy, wields a cold, blunt demeanor and lightning-fast reflexes. Her short black hair and casual blue hoodie paired with black shorts contrast her polished public persona, while a fox mask cloaks her celebrity identity during competitions. Her chaotic apartment, cluttered and neglected, mirrors her indifference to domestic order.

Childhood struggles drove Yū to seek refuge in online gaming, where she forged a pivotal bond with Shun Tokinoya under the alias "Explosion-kun." His unwavering support during her darkest days anchored her emotional growth, though their connection fractured after his father’s death. Years later, she reignites his competitive fire by challenging him in *Xaxxerion*, joining his team, Fox One, as "Phantom Ninja." Her acting-trained self-defense skills surface when confronting intruders like Shun and Akito, whom she swiftly subdues.

Beneath sarcastic banter and playful jabs lies Yū’s unspoken affection for Shun. She preserves their bond through covert gaming sessions as Explosion-kun, deliberately maintaining a broken microphone to hide her voice. Her loyalty falters upon overhearing Shun prioritize his sister Mio, sparking doubts about her role as his "backup." This turmoil drives her to shed anonymity during a high-stakes tournament, publicly unmasking to embrace her dual identity—gamer and actress—despite career risks. Though fan reactions split, her resolve hardens to pursue esports authentically.

Guided by manager Emiko Takanashi, Yū navigates the fallout of her revelation, reconciling her fractured identities. She evolves from secrecy to transparency, trading solitary pride for teamwork. By the series’ end, she emerges as both a celebrated actress and a respected esports contender, defying expectations to embody a multifaceted legacy forged through vulnerability and resilience.