 If you liked
Metropolis
|
 ...then you might like
Project BLUE Chikyuu SOS
|
Both titles show some inspiration from Fritz Lang's Metropolis to a greater (Metropolis) or lesser (Project Blue Chikyuu) extent, and have a boy discovering the secrets behind recent events, with quite some action.
If you like an adventure story in a retro futuristc setting, these titles may be for you.