"Turn A Gundam: Moonlight Butterfly" is a two-episode OVA that serves as a condensed retelling of the events from the 1999 anime series "Turn A Gundam," directed by Yoshiyuki Tomino. The OVA focuses on the central conflict between Earth and the Moonrace, a group of humans who fled to the Moon centuries ago and now seek to return to Earth. The story is set in a post-apocalyptic world where advanced technology is largely forgotten, and society has regressed to an early 20th-century level of development.

The narrative centers on Loran Cehack, a young Moonrace scout sent to Earth to assess its suitability for colonization. Disguised as a humble Earthnoid, Loran integrates into the Heim family and becomes a mechanic. When the Moonrace begins its invasion, Loran discovers the Turn A Gundam, a highly advanced mobile suit buried underground. Reluctantly, he pilots the Gundam to protect Earth and its inhabitants, despite his loyalty to the Moonrace. The Turn A Gundam is revealed to be a relic of a catastrophic war that devastated Earth millennia ago, and its activation raises fears of history repeating itself.

The Moonrace, led by figures like Gym Ghingnham and Dianna Soreil, seeks to reclaim Earth, believing it to be their ancestral home. Gym, a charismatic and ruthless leader, desires to use the Turn A Gundam's destructive power to assert dominance. Dianna, the Moonrace's queen, initially supports colonization but grows conflicted as she witnesses the suffering caused by the conflict. Loran's dual identity as both a Moonrace scout and an Earthnoid ally places him at the heart of the struggle, forcing him to navigate complex moral dilemmas.

The OVA highlights the escalating tensions between the Earthnoids and the Moonrace, culminating in the activation of the Turn A Gundam's ultimate weapon, the Moonlight Butterfly. This devastating system unleashes self-replicating nanomachines capable of destroying all technology and civilization, symbolizing the cyclical nature of war and destruction. Loran and his allies strive to prevent the weapon's full activation, seeking a peaceful resolution to the conflict.

Key characters include Loran, whose idealism and empathy drive his actions; Dianna, whose leadership is tested by the ethical implications of colonization; and Gym, whose ambition and ruthlessness make him a formidable antagonist. The OVA condenses the series' themes of war, reconciliation, and the consequences of technological advancement, offering a streamlined yet impactful narrative. The Moonlight Butterfly serves as both a literal and metaphorical device, representing the potential for annihilation and the hope for renewal, as the story explores the possibility of coexistence between Earthnoids and the Moonrace.