Midi Plenmatz is a scion of Fedovar's ruling Plenmatz family, directly connected to its leader, Tonodono Plenmatz. She accompanied Gold to Fedovar to investigate the assassination attempt on his father, Retklaad Dithersmount, one of the five Overseers governing the EDO system. During this investigation, Midi met Ritt, Ebota's son, who had been independently researching the circumstances of Retklaad's near-fatal incident.

A central element of Midi's background is the Plenmatz family tragedy. Her relatives, including Tonodono Plenmatz, his wife, and their son Ion, perished during a test flight of the Ovaconia spacecraft. The craft malfunctioned and crashed under Retklaad's supervision, triggering subsequent suicides and fatal accidents among those associated with the ship and the family. Following Gold's apparent death during a confrontation at the Plenmatz abandoned mansion, Midi returned to Ritt's house distraught and struggling to accept his demise, maintaining hope for his survival for days.

Midi later witnessed a televised news report announcing Gold's unexpected reappearance and his appointment as a new Overseer. In the report, Gold publicly accused Retklaad of involvement in a conspiracy to eliminate the Plenmatz family, claiming Ion had been murdered. This accusation forced the other Overseers to initiate a trial for Retklaad, despite their apparent prior knowledge of the conspiracy. Midi's involvement persisted as the investigation uncovered deeper truths linking the Ovaconia crash and the conspiracy to the EDO system's foundational reliance.