Here is the story synopsis, via VNDB:
Let’s set out to find a real treasure.
Tyler is a high school student who is obsessed with geohunting, a GPS-based treasure hunting game. One day during summer vacation, Tyler and his friends get drawn into a mysterious incident while out treasure-hunting. The real and imagined become interconnected. Thoughts are thrown into chaos. Tomorrow becomes today.
Swallowed up by a time vortex, they are trapped in a never-ending time loop, repeating “today” again and again.
Then they meet other “loopers.” Simon, the leader, and the mysterious girl Mia. If they join forces, will they be able to break out from this eternal prison…?