When @Dagon's domain collapses following his death, the barrier does simply vanishes, compressing the tropical beach, the ocean, and the torii gate into a single point before releasing. Everyone inside the domain is expelled not randomly, but returns specifically to the @Third Basement Level (B3F) of @Shibuya Station on, the exact location where @Dagon first manifested his domain and pulled them inside.
This occurs because the domain was anchored to that specific physical space on B3F when it was activated. The cursed energy that constructed the pocket dimension extended outward from Dagon's position on the Den-en-toshi Line platform, wrapping around the sorcerers and pulling them into a separate space while leaving a metaphysical tether to the original location. When Dagon dies, that tether snaps, and the domain's internal space collapses backward along the path it was created, funneling everything inside back to the point of origin.
The transition is abrupt and disorienting. One moment the survivors stand on white sand beneath an artificial sun, the next they find themselves stumbling onto the familiar tile floor of the B3F platform. The green line markings of the Den-en-toshi Line are beneath their feet, the concrete pillars they initially hid behind are around them, and the dim emergency lighting of the underground station flickers overhead. The sudden shift in pressure leaves ears ringing and vision swimming as reality reasserts itself.
For those who were deep within the domain—near the torii gate or far out in the ocean—the sensation is more violent. They are thrown forward as if caught in a wave, tumbling across the platform until they collide with pillars, benches, or the platform edge doors. The shikigami that still existed within the domain at the moment of collapse dissolve into streams of cursed energy that scatter and fade into the station air, leaving behind only the faint smell of salt and ozone.
When the last traces of the tropical beach disappear and the final echoes of crashing waves fade to silence, those who survive find themselves standing on the same B3F platform where the battle began. The space around them is exactly as it was before the domain engulfed them—the same pillars, the same signage, the same tiled floors—but now marked by the aftermath of their struggle. Nanami, Maki, Naobito, and Megumi are all deposited here, along with the corpse of Dagon, which materializes as a crumbling, dissolving form on the platform floor. The only difference is the absence of the hole Megumi tore in the domain's barrier, as that wound existed only within the pocket dimension and does not translate back to the real world.