Youji Haneda endured deep childhood trauma stemming from his mother's resentment, as she saw him solely as an extension of her despised ex-husband. This toxicity shadowed them even after moving in with her brother, whose daughter Kobato was Youji's age. His mother actively prevented closeness between the cousins, culminating in a critical incident that inflicted profound trauma on Youji. The psychological pain drove him to withdraw completely, sealing himself away within his subconscious to escape the unbearable memories.

This dissociation fractured his psyche, giving rise to multiple distinct personalities to manage reality. Takashi Haneda emerged as a helpful and friendly persona, blissfully unaware of the past trauma. Two further personalities, Hayato Narita and Shūsuke Chitose, developed to shoulder responsibilities Takashi couldn't handle, particularly those concerning Kobato, who remained Youji's vital connection. A fourth personality, Itami Karura, surfaced as unstable and aggressive. Together, these five distinct identities coexisted within Youji's single physical form.

Youji remained secluded until Takashi, aided by Kobato, began confronting the suppressed memories. This therapeutic process unlocked the past, enabling Youji to reemerge and reclaim control of his body. His other personalities did not vanish but retreated into the background. Despite the extraordinary nature of his return, Youji adapted to daily life with relative speed. He retained full access to the memories and experiences of all his alternate personalities, easing his reintegration. Emerging from his long isolation, Youji displayed an open-hearted and optimistic demeanor, firmly focused on future possibilities.