Akira Mizutamari is a robotics genius who achieved breakthrough success by developing and commercializing SALT, a multitask robot assistant designed for daily life support. Following this, he stalled creatively as subsequent inventions failed to progress. Upon hearing his friend Kunihito Obayashi suggest that romantic relationships enhance capabilities, Mizutamari interprets the advice literally. He resolves to scientifically create an artificial girlfriend to overcome his research impasse, leading to the development of the advanced android designated "No. Zero," whom he brings to life.

Initially approaching the project with clinical detachment, Mizutamari shows no inherent interest in love or interpersonal connections. His underdeveloped social skills leave him unaccustomed to meaningful communication. However, living alongside No. Zero gradually unsettles his emotions, triggering internal conflicts and unexpected emotional shifts that challenge his detached perspective.

Their evolving relationship is marked by significant misunderstandings and complexities, stemming from his struggle to reconcile his logical, scientific mindset with the emerging emotional dynamics between them. Their interactions reveal deeper layers of his character, including connections to influential figures from his past whose intentions or calculations may have shaped his path. He belongs to a familial structure indicated by the relative Inaba Mizutamari. His journey culminates in unforeseen turns that fundamentally alter his relationship with No. Zero, steering their story toward an unexpected resolution reflecting his internal transformation.