Arata naru Sekai: Mirai-hen

Four students in school uniforms walk in silence across a desolate landscape. They are time travelers who were sent 6000 years ahead from a present trapped in an endless cycle of the same day, to escape humanity's extinction. They learned about time travel at school, passed an aptitude test, and were dispatched to the future as instructed. Uncertain of their next steps, they carry only a small, toy-like cellphone with a light, which is useless without a signal. During their walk, they observe unusual birds in the sky and a river with an odd color in the distance. One of them discovers a deserted house and notices a name carved into the gate.