Digimon Adventure:

In 2020, everyday life depends on a digital network connecting almost everything from transportation to communication. Humans do not realize that behind this network exists a Digital World inhabited by creatures called Digimon. When Tokyo's systems begin failing and Taichi's mother and sister Hikari become trapped on a runaway train, he rushes to reach them and is suddenly transported into the network, where he meets Agumon. Taichi quickly learns that disasters in the real world are connected to battles taking place on the digital side. As other children and their partner Digimon appear, a new adventure begins in which saving a city, or even far more, depends on what happens inside a world most humans cannot see.