ATOM: The Beginning

In the near future, Japan was struck by a catastrophe of unknown origin. Five years later, as Japan is undergoing reconstruction, two young researchers at a university are putting everything they have into developing a robot...

Note:
The manga tells the story of what happens up until the birth of Astro Boy and it can be considered an "episode zero" story.

Links:

• Kasahara's Twitter
• Anime on ANN