Maboroshi

Young Masamune's life is a normal one. He goes to school, hangs out with friends, and practices drawing in his rural Japanese town. But then everything changes for the surreal. When an explosion at the local steelworks factory literally shatters the sky, the town is cut off from the rest of Japan, the seasons cease to change, and people stop aging. Everyone tries to continue on as normal—hoping that if they hold on long enough, the world will right itself. Yet, as the days pass, nothing changes—until the day Masamune's classmate Mutsumi sneaks him into the factory to help her take care of the mysterious feral girl living there.

Synopsis from Anime News Network