"Dallos" is a four-episode OVA series set in a future where humanity has colonized the Moon. The story centers on the conflict between the lunar colonists, who live in harsh conditions and rely on mining operations for survival, and the Earth government, which exploits their labor and resources. The colonists, led by a young man named Shun Nonomura, grow increasingly resentful of Earth's oppressive control. Shun, along with his brother Big Al and their friend Doru, becomes involved in a resistance movement seeking independence and better living conditions.

The narrative explores themes of rebellion, class struggle, and the moral complexities of revolution. Shun is initially hesitant to join the resistance but is driven to action after witnessing the suffering of his people and the brutal tactics employed by Earth's forces. The Earth government, represented by Commander Gibson and his enforcer, the cyborg dog Raider, seeks to maintain control through intimidation and violence. The colonists' resistance is further complicated by the presence of Dallos, a mysterious ancient structure buried beneath the Moon's surface. Dallos is believed to hold immense power, and both sides vie for control over it, believing it could tip the balance in their favor.

As tensions escalate, Shun and his allies uncover secrets about Dallos and its connection to the Moon's history. The series delves into the ethical dilemmas faced by both the colonists and the Earth forces, highlighting the human cost of conflict. The characters grapple with questions of loyalty, sacrifice, and the pursuit of justice, as the struggle for freedom becomes increasingly desperate. The story culminates in a climactic confrontation that forces both sides to confront the consequences of their actions, leaving the fate of the Moon and its inhabitants uncertain.