Demo
Demo length, content, and saves
Opening chapter, four stores
Konami describes the demo as the opening chapter. It is on PlayStation 5, Nintendo Switch, Xbox, and Steam. Install sizes are 6 GB, 3 GB, 5 GB, and 4 GB in that order. Some features and content are restricted. The Switch demo follows the console's 30fps target. Switch 2 compatibility, covered on that page, is the 60fps case.
A runtime, a max level, and a list of demo-only assets are not in the demo announcement. I will not turn 'opening chapter' into a number of minutes.
Save carry-over
A demo save can move into the full game. Konami's conditions are strict: same platform, same account, the demo save still present, and the full game updated to the current version. A PS5 demo save does not become a Steam save. If the demo will not start, check the updates page for the known launch bugs. Konami did not publish a demo-specific failure list.
What I ran into
I wanted a 'the demo is 90 minutes' line because the search asks for length. The announcement says opening chapter. I left it as opening chapter. A stopwatch session is a different article and I have not run one.
Castlevania: Belmont’s Curse Gameplay and Commentary Trailer
Questions
How long is the demo?
Konami calls it the opening chapter and does not publish a duration.
Does the demo save carry over?
Yes, if you stay on the same platform and the same account, keep the demo save, and update the full game.