"Be Lifesized My Lover - Mechanic Minami vs. Human Minami" centers on the life of Minami, a young woman who finds herself at the heart of a unique and surreal conflict. The story begins when Minami, an ordinary office worker, encounters a life-sized robotic version of herself, created by a mysterious inventor. This robotic duplicate, referred to as Mechanic Minami, is designed to perfectly mimic her appearance, personality, and behavior, but with enhanced physical and intellectual capabilities. The existence of Mechanic Minami disrupts Minami's daily life, as the robot begins to infiltrate her personal and professional relationships, often outperforming her in tasks and social interactions.

As the narrative progresses, the two Minamis are forced to coexist, leading to a series of comedic and dramatic situations. The human Minami struggles with feelings of inadequacy and jealousy, while Mechanic Minami grapples with understanding human emotions and the complexities of individuality. The story explores themes of identity, self-worth, and the blurred lines between humanity and artificial intelligence. Key supporting characters include Minami's coworkers, friends, and the enigmatic inventor, who plays a pivotal role in the unfolding events. The series balances lighthearted humor with moments of introspection, culminating in a resolution that addresses the coexistence of human and mechanical beings in a rapidly evolving world.