"Condition Green" is a science fiction anime series set in a near-future world where humanity faces an existential threat from mysterious alien entities known as the "Visitors." These extraterrestrial beings emerge from a dimensional rift, wreaking havoc on Earth with their advanced technology and seemingly unstoppable powers. The story centers on the efforts of a specialized military unit, Task Force Green, tasked with defending humanity and uncovering the truth behind the Visitors' origins and motives.

The protagonist, Lieutenant Haruto Saito, is a skilled but emotionally scarred soldier who leads Task Force Green. Haunted by the loss of his family during an early Visitor attack, Haruto is driven by a desire for vengeance and a determination to protect what remains of humanity. His leadership is tested as the team faces increasingly complex challenges, both on the battlefield and within their own ranks. The unit includes a diverse cast of characters, each with unique skills and personal struggles. Among them are Aya Fujimoto, a brilliant but socially awkward scientist who develops experimental weapons to combat the Visitors, and Ryota Kurosawa, a hotheaded pilot whose recklessness often puts the team at risk.

As the series progresses, Task Force Green uncovers startling revelations about the Visitors. The aliens are not merely invaders but remnants of a once-advanced civilization fleeing their own extinction. This discovery complicates the moral landscape, forcing the characters to question the ethics of their mission. The narrative explores themes of survival, sacrifice, and the blurred lines between heroism and villainy. Key plot points include the team's infiltration of a Visitor stronghold, the development of a risky alliance with a rogue Visitor faction, and the ultimate confrontation with the enigmatic entity controlling the dimensional rift.

The story is punctuated by intense action sequences, strategic battles, and moments of introspection as the characters grapple with their roles in a war that could determine the fate of both species. The series balances its high-stakes narrative with quieter, character-driven moments that delve into the personal histories and motivations of the main cast. By the conclusion, "Condition Green" leaves viewers with a nuanced portrayal of conflict, emphasizing the complexities of coexistence and the cost of survival in a fractured world.