It was serialized in Kodansha's Monthly Afternoon magazine from June 1994 to February 2006, with a concluding postscript episode in July 2006, and collected in 14 tankōbon volumes.

Exactly what happened is never explained, but sea levels have risen significantly, inundating coastal cities such as Yokohama, Mount Fuji erupted in living memory, and climate change has occurred.

Whole chapters are devoted to brewing coffee, taking photographs, or repairing a tiny model aircraft engine, sometimes with only a few lines of dialogue.

Through Alpha's experiences, the author brings out the small wonders of everyday life and makes the reader aware of their passing: the aircraft engine runs out of fuel; her scooter breaks down; the rising ocean encroaches on her coffee shop; the neighborhood children she loves grow up and move away.

[6][7] Ashinano explains few details of Alpha's world, leaving mysteries that engage the reader[9] as the series unfolds in a meandering progression, by turns funny, touching, and nostalgic.

For example, there is a bus stop named Koumi'ishi to the south of Hayama, and Atsugi airfield, where Alpha meets Nai, is located in Ayase.

That several details of Yokohama Kaidashi Kikou are left unexplained, or have answers only hinted at, is frequently mentioned in reviews of the series as contributing to a tone of mystery.

Among the most prominent are: Comparisons have been made between Yokohama Kaidashi Kikou and Aria, noting that they are both quiet slice-of-life stories in a futuristic setting with a similar emotional effect.

[23][24] A reviewer at Uknighted Manganime wrote, "What the two have in common, though, is a bright look at the future and a generally optimistic view of humanity, despite our failings.

"[25] A total of 140 chapters were published in Japan by Kodansha in the seinen (aimed at younger adult men) manga magazine Monthly Afternoon between June 1994 to February 2006.

[49] Set long after the conclusion of the manga series, it tells the story of a boy robot named Omega and his search for the legendary Cafe Alpha.