After G. Gardevoir is kidnapped, go to the Grand Gates (south of the Nature Center), to the left room with the gear, and follow the path until you find the Arc. I won't give spoilers, but once you win this fight for Gardevoir, you leave the Arc and return to the Inside of the Grand Gate. It will be opened, and you can move freely between Route 1 and North Obsidia Ward. To be put simply, you don't need to go through the escapade path to access Route 1 if you continue the storyline