Daedalus hails from Synapse, an advanced realm existing above Earth. Over eons, she evolved alongside its inhabitants, developing technology indistinguishable from magic to humans. As Synapse's foremost scientist, she created the Rule, a wish-granting system that initially brought happiness but ultimately triggered widespread existential crises and mass suicides, collapsing the population to three thousand. Seeking a solution, she recreated the universe. When this failed to resolve Synapse's discontent, she created humans and the first-generation Angeloids for amusement, collaborating with her research partner Minos. Observing humans, she and other Synapse residents grew envious of human dreaming capabilities. They entered a dream-like state by projecting their consciousness into artificial human bodies on Earth.

Within this dream, she lived as Sohara Mitsuki, Tomoki Sakurai's childhood friend. During this time, she formed a deep bond with Tomoki before her dream persona succumbed to a young death from illness, erasing her from human memories. Unable to return to the dream without causing Tomoki distress, she created a clone of her dream self—the Sohara Mitsuki seen throughout the series—to ensure Tomoki would not forget her.

She frequently manifests in Tomoki's dreams, presenting herself as a lover figure but vanishing upon his waking, leaving him distressed. Her primary motive for contacting him is to seek help for herself and her "daughters"—the first-generation Angeloids she created, including Ikaros, Nymph, Astraea, the Harpies, and likely Oregano. She sends these Angeloids to Tomoki under the pretext of them being "captured by the sky," hoping they will gain freedom through his influence. Her dream interactions often involve warnings about impending dangers.

Physically resembling her dream persona Sohara with long blue hair and similar height, Daedalus possesses white wings and a more voluptuous figure. She typically appears barefoot and travels on a cloud-like machine due to weak health. The manga uniquely depicts her with four wings, while the anime shows two wings consistent with other Synapse residents.

Throughout events, she collaborates with Eishiro Sugata during his visits to Synapse. She intervenes to save Sugata from the Harpies, demonstrating protective instincts despite her usual passivity. She expresses outrage when Minos forcibly converts Hiyori Kazane into an Angeloid, highlighting her disdain for his methods. Her scientific contributions include installing the Pandora system in first-generation Angeloids, enabling Ikaros to overpower Melan Angeloids during conflict.

Her true identity as the original Sohara is revealed in the final arc, clarifying her emotional connection to Tomoki and her motivations for entrusting him with the Angeloids. She maintains a calm, caring personality, treating the Angeloids as her daughters and showing concern for Synapse's inhabitants. Her intelligence remains unparalleled in Synapse, rivaled only by Minos. Lacking overt combat abilities, she relies on strategic interventions like creating portals or utilizing her dream-visitation capability.

Her relationship with Minos deteriorates from research partners to enemies due to his cruelty. She harbors deep affection for Tomoki, rooted in their shared past. The creation of the Sohara clone and her persistent efforts to protect Tomoki and the Angeloids underscore her commitment to preserving their connections despite her existence in Synapse.