It will probably be an isekai.
Modern boy teleported to medieval fantasy world, defeats evil dude, saves princess and is forced back to his world.
Turns out it was all a dream. Or was it?
When climbing some random long-ass staircase he bumps into some random girl that looks the same as the princess he saved back in the other world.
Screen fades to black, roll credits.
Play "Smash Mouth - All Star".