Digimon Adventure:

It's the year 2020. The Network has become something humans can no longer do without in their daily lives. But what humans don't know is that on the other side of the Network is the Digital World, a realm of light and darkness. Nor are they aware of the Digimon who live there.
Fifth grader Taichi Yagami]s mother and little sister Hikari went to Shibuya, and now they're aboard a runaway train. Taichi hurries to Shibuya to save his mother and sister, but the instant he heads toward the station platform... a strange phenomenon befalls the DigiDestined, and Taichi goes to the Digital World!