Planetarian: Storyteller of the Stars

In the future after much of the world has been devastated by nuclear and biological warfare, a young scavenger or 'Junker' exploring a quarantined and abandoned city comes across a service robot still faithfully awaiting customers in the rooftop planetarium of a department store. Against his pragmatic instincts he helps the robot repair the planetarium's projector: a decision which will change both their fates.

(Source: Anime News Network)

Note: Planetarian: Hoshi no Hito combines the story of the original work with an expansion that extends the narrative with content from the 'Hoshi no Hito' light novel sequel.