Emi Kaido, a lonely 17-year-old living alone in Shibuya, Tokyo after her father's unexplained disappearance, copes with detachment through listless behavior and seeking dangerous situations. This recklessness leads her to discover the "Case," an artifact granting wishes that manifests for her as a large pencil, symbolizing her desire for creative expression through drawing.

Her discovery coincides with the arrival of four heroes from destroyed alternate dimensions: Ken Washio, Jouji Minami, Takeshi Yoroi, and Tetsuya Azuma. They pursue "Z," the entity responsible for their worlds' destruction, later revealed to be Emi's father, Kazumichi Kaido. Z's research showed Emi meeting tragic fates in every parallel world; to save her, he sealed her in a protected reality and used the Case to eliminate other worlds, believing this ensured her survival.

Emi grapples with this revelation about her father's identity and motives. Her relationship with the heroes evolves as they unite to confront Z and restore the destroyed worlds, with Emi central to their mission as the holder of the Case. Thirteen months after resolving the conflict with Z, Ken returns seeking Emi's help. An incarnation of the Case, the "Nexus," causes instability in an alternate version of his world ruled by a corrupted Dr. Nambu. Emi accompanies Ken and the heroes to confront this new threat. The artifact consistently manifests as a pencil for Emi, symbolizing her connection to creation and the unresolved consequences of her father's actions across dimensions.