"The Super Dimension Cavalry Southern Cross" is set in the year 2120, on the planet Gloire, a distant colony of humanity. The story unfolds as the planet faces an invasion by the Zor, a mysterious alien race seeking to reclaim Gloire, which they believe is their ancestral home. The Zor are led by the enigmatic Jeanne Francaix, who commands their forces with a mix of advanced technology and psychic abilities. The human colonists, unprepared for such a conflict, rely on the 15th Southern Cross Army, a military unit equipped with advanced mecha known as Spartas, to defend their territory.

The protagonist, Jeanne Montagne, is a young and inexperienced officer in the Southern Cross Army. Despite her initial lack of confidence, Jeanne grows into her role as a leader, driven by her determination to protect her comrades and the colony. Her journey is marked by personal struggles, including her complicated relationship with her superior, Colonel Alan Johnson, and her growing awareness of the moral complexities of war. The narrative explores themes of identity, loyalty, and the cost of conflict, as Jeanne and her fellow soldiers grapple with the realities of fighting an enemy whose motivations are not entirely clear.

The Zor, while initially portrayed as antagonists, are gradually revealed to have their own reasons for reclaiming Gloire, rooted in their history and culture. This adds depth to the conflict, as the humans begin to question the righteousness of their own cause. The series delves into the psychological toll of war on both sides, with characters on each side experiencing loss, doubt, and moments of empathy for their enemies.

Key supporting characters include Marie Angel, a skilled pilot and Jeanne's close friend, who provides emotional support and camaraderie; Bowie Emerson, a talented but reckless soldier whose actions often put him at odds with his superiors; and Seifriet Weiße, a Zor commander who becomes a recurring adversary for Jeanne. The interactions between these characters drive much of the narrative, highlighting the personal stakes of the larger conflict.

As the war intensifies, the Southern Cross Army faces increasingly difficult challenges, including internal dissent, resource shortages, and the Zor's relentless attacks. The series builds toward a climactic confrontation that forces both sides to confront the consequences of their actions. The resolution of the conflict is bittersweet, with sacrifices made on both sides and no clear victor, underscoring the futility and tragedy of war.

"The Super Dimension Cavalry Southern Cross" combines mecha action with a thoughtful exploration of its characters' inner lives and the broader implications of their struggle. The series stands out for its nuanced portrayal of war and its impact on individuals, offering a narrative that is both engaging and thought-provoking.