|This article is about a/an event in Kamen Rider Build.|
- "It has been 10 years since Pandora Box was discovered on Mars and caused the Sky Wall tragedy. Our country was divided into Touto, Seito and Hokuto, resulting in untold chaos."
- ―Simply introduction by Narrator in opening theme.[src]
The Sky Wall Disaster (スカイウォールの惨劇 Sukai Wōru no Sangeki) was an unprecedented incident that occurred 10 years prior to the start of Kamen Rider Build's events when Evolto attempted to raise Pandora's Tower by using his powers on the box. However due to Vernage's tampering with the bottles, he failed and the box caused the Sky Wall to spring pre-constructed from the ground, instead.
The rising wall suspended several people helplessly in the air with an unspecified fate, and the entire country of Japan was split into three parts: Hokuto, Touto, and Seito. Everyone present at the event was noted by Director Gentoku Himuro to have suddenly changed their personalities to be much more aggressive.
With the nation divided, several foreign powers have tried to take advantage of the disarray of Japan and claim/annex parts of the nation through imperialistic influence, though the "vultures", as they are called by Director Himuro, are being kept at bay for now as none of the districts have any interest in allying or being influenced by any other nation (especially Russia and China).
Behind the scenes
The Sky Wall Disaster serves as the opening event of Kamen Rider Build, until episode 28. The ramifications of the Sky Wall Disaster explicitly sets Build apart from the prior Kamen Rider Series; ultimately, the film Kamen Rider Heisei Generations FINAL: Build & Ex-Aid with Legend Riders confirmed that Build took place in its own reality.
South Korean dub
Most South Korean dubs of Kamen Rider relocate the show's setting from Japan to South Korea. However due to the current political regime of both North and South Korea, the show was based on a fictional island nation (loosely based on the United States and Canada) instead.