"Fafner in the Azure - Right of Left" is a prequel to the main series "Fafner in the Azure," set in a world where humanity faces an existential threat from mysterious alien entities known as Festum. The story takes place on Tatsumiyajima, a remote island that serves as a sanctuary for humans protected by the advanced mecha units called Fafners. These machines are humanity's only defense against the Festum, which seek to assimilate all life forms.

The narrative centers on the 12th Strategic Armored Troop, a group of young pilots tasked with operating the Fafners. The protagonist, Ryou Masaoka, is a skilled pilot and the son of the island's chief engineer. Alongside him is Soushi Minashiro, a reserved and enigmatic boy who shares a deep connection with the Fafner system. The story explores their struggles as they prepare for an impending Festum invasion, delving into the emotional and psychological toll of their responsibilities.

As the Festum breach the island's defenses, the pilots are forced to confront the harsh realities of war. The narrative highlights the sacrifices made by the young soldiers, particularly Ryou, who grapples with the weight of leadership and the loss of comrades. Soushi's role becomes increasingly pivotal as his unique abilities and connection to the Fafner system are revealed, hinting at a greater destiny tied to humanity's survival.

The series also examines the broader societal implications of the conflict, including the ethical dilemmas surrounding the use of child soldiers and the moral ambiguity of the Fafner program. The island's leadership, including Ryou's father, faces criticism for their decisions, adding layers of tension and complexity to the story.

"Right of Left" serves as a poignant exploration of themes such as sacrifice, camaraderie, and the human cost of war, while setting the stage for the events of the main series. It provides crucial backstory for key characters and the world they inhabit, offering a deeper understanding of the stakes and emotional underpinnings of the larger narrative.