Miru emerges as a central, enigmatic presence within the desolate crater formed by "Skyfall," the catastrophic destruction and crash of an orbital space colony onto Earth. This ruined landscape is now inhabited by genetically warped creatures known as Kaiju. She is unexpectedly encountered within this hazardous zone by Ray, an avatar descending to collect scattered "seeds," unaware of the area's full dangers and significance. Her sudden appearance instantly marks her as a figure of profound mystery.

The core narrative question revolves entirely around her true nature and origin. It is deliberately ambiguous whether she is human or possesses some connection to the Kaiju inhabiting the crater. This uncertainty – human or Kaiju – forms the central mystery driving Ray's interactions. She is also identified by the alternative name Mildred in some references, a detail offering no further context about her background or role.

Her story begins and ends within the crater's confines as established in the initial animated short film narrative. Information regarding her specific origins, background story, or character development across any official media, including sequels, spin-offs, or expanded universe content like the mixed reality game "KAIJU DECODE -super multiverse MR-," remains absent. Her role and characteristics are defined solely by this context.