The man, known simply as "the junker", stays with this robot for a time and attempts to fix the projector of the planetarium where the story takes place.

A light novel of short stories set in the world of Planetarian was released in April 2006, and three audio dramas have also been produced.

Planetarian's story, artwork and music have been praised, and the PS2 version ranked first for console games in terms of satisfaction in 2007.

[2] It is said that due to the depletion of natural resources, overpopulation, and the failure of the Space Exploration Project, humanity has virtually eradicated itself through biological and nuclear warfare, turning a once prosperous civilization into complete ruin, cast in darkness and poisoned by constant rain[3] from nuclear fallout.

[2] The main location where most of the story takes place is the fictional Flowercrest Department Store in a derelict city.

It is based on the real Matsubishi Department Store of Hamamatsu, Shizuoka in Japan,[4] although the planetarium on the rooftop is fictitious.

[2] While dodging detection from war machines in a ruined city, the protagonist enters a building with a dome on the roof to search for usable supplies.

A machine the protagonist calls a fiddler crab, due to its design, is guarding the entrance to the city in which he came from, and he devises a plan to destroy it armed with only a grenade launcher.

Yumemi spends her emergency battery life replaying her pre-war memories to the protagonist using a tiny holographic projector on her ear.

In her final moment as she "dies" in front of him, Yumemi ejects the memory card from her artificial brain for his safekeeping.

Touched and completely shaken by the loss of the beautiful world she left in his mind, he throws away his gun and puts the memory card in his coat, before wandering off with a broken leg as the fallen war machine's automated backup units are closing in on the scene.

Planetarian is Key's fourth visual novel, and had a small staff of three main people that did the majority of the work for the game's first release.

The Planetarian Original Soundtrack was released on August 11, 2006, at Comiket 70 by Key Sounds Label; it was later re-released on December 28, 2006.

[17] Another updated version compatible for Windows 7 PCs called Planetarian: The Reverie of a Little Planet Memorial Edition was released on April 30, 2010.

[19] Planetarian was released on Steam by Sekai Project in English for Windows on September 12, 2014,[20] with later support planned for macOS and Linux devices.

[10][24] A version playable on FOMA and SoftBank 3G mobile phones was released by Prototype through Visual Arts Motto on November 28, 2006.

[40][41] Visual Arts launched a crowdfunding campaign on November 29, 2019, to produce an original video animation (OVA) episode titled Planetarian: Snow Globe.

[42] By the end of the campaign, the final stretch goal had been achieved for Key to produce a kinetic novel version of Planetarian: Snow Globe for Windows.

[44] The staff for Snow Globe was the same for The Reverie of a Little Planet with the scenario written by Yūichi Suzumoto and the art by Eeji Komatsu.

[52] Three drama CDs were released by Key Sounds Label based on the short stories in the light novel.

[53][54][55] The opening track takes place one year before the protagonist arrives at the planetarium and the "Snow Globe" story is told as a flashback.

[57] A five-episode original net animation (ONA) adaptation was produced by David Production and directed by Naokatsu Tsuda.

A single titled "Twinkle Starlight / Worlds Pain" performed by Sasaki and Ceui was released on July 27, 2016.

[59] The same staff also produced an anime film titled Planetarian: Storyteller of the Stars that premiered in Japanese theaters on September 3, 2016.

[62] Visual Arts launched a crowdfunding campaign on November 29, 2019, to produce an original video animation (OVA) episode titled Planetarian: Snow Globe.

[42] People who backed the campaign received a copy of the OVA on Blu-ray in January 2021,[63] and it was released to the general public on August 25, 2021.

[69] When the PSP version was re-released as a fundraising event for the 2011 Tōhoku earthquake and tsunami, 16,663 units were pre-ordered by the day of its release on May 12, 2011.