"Sonic Soldier Borgman: Lover's Rain" is a two-episode OVA that serves as a sequel to the original "Sonic Soldier Borgman" series. The story is set in a futuristic world where humanity faces threats from the malevolent Gargan Empire, an alien force seeking to conquer Earth. The narrative centers on Ryo Hibiki, a young man who pilots the powerful Borgman armor, a mechanized suit designed to combat the Gargan Empire. Alongside him are his allies, Anice Farm and Chuck Sweagger, who also operate Borgman units. Together, they form a resistance force dedicated to protecting humanity.

The OVA begins with the Gargan Empire launching a new wave of attacks, targeting Earth with advanced weaponry and strategies. Ryo and his team are called into action to counter these threats, but the conflict becomes more personal when Anice is captured by the enemy. Her abduction reveals deeper layers of the Gargan Empire's plans, including experiments to harness human emotions as a weapon. The story explores themes of loyalty, sacrifice, and the emotional toll of war, as Ryo and Chuck must navigate both external battles and internal struggles to rescue Anice and thwart the Empire's schemes.

Key characters include Ryo Hibiki, the determined and skilled protagonist; Anice Farm, a compassionate and resourceful pilot whose capture drives much of the plot; and Chuck Sweagger, a loyal and pragmatic ally who provides tactical support. The Gargan Empire is represented by its enigmatic leaders, who employ psychological manipulation and advanced technology to achieve their goals. The OVA delves into the relationships between the main characters, particularly the bond between Ryo and Anice, which is tested under the strain of their mission.

The narrative is driven by a mix of intense mecha battles and emotional moments, balancing action with character development. The OVA concludes with a resolution to the immediate conflict, though it leaves room for reflection on the ongoing struggle against the Gargan Empire and the personal costs of war. The story maintains a focus on the human element within a sci-fi setting, emphasizing the resilience and determination of its protagonists in the face of overwhelming odds.