"planetarian: Snow Globe" is a short anime series that serves as a prequel to the original "planetarian" story, expanding on the backstory of the character Yumemi Hoshino, an android guide at the Hoshizora Planetarium. Set in a post-apocalyptic world where humanity has been decimated by war and environmental collapse, the narrative unfolds in a city buried under perpetual snowfall. The story centers on Yumemi's daily routine as she continues to operate the planetarium despite the absence of visitors, maintaining her programming to provide tours and presentations.

The plot explores Yumemi's unwavering dedication to her role, even as the world around her deteriorates. Her interactions with a mysterious maintenance worker, who occasionally visits the planetarium, provide glimpses into the broader context of the ruined city and the struggles of the few remaining humans. The worker, though initially indifferent, gradually becomes intrigued by Yumemi's persistence and optimism, leading to moments of quiet reflection on the nature of humanity and artificial intelligence.

The series delves into themes of loneliness, perseverance, and the enduring hope for connection in a desolate world. Yumemi's character embodies the innocence and idealism of a machine programmed to serve, contrasting with the bleak reality of her surroundings. The narrative is driven by her interactions with the worker and her internal monologues, which reveal her programmed purpose and her subtle longing for human interaction. The story culminates in a poignant exploration of the relationship between humans and machines, set against the backdrop of a world that has largely forgotten the stars.