Open Watch now, pick a service, and use its Download arrow beside each episode or for the whole season. The episodes stay in that service's app for weeks and play offline, ideal for a flight or a commute.
How much space
An hour of standard quality takes about half a gigabyte and an hour of HD one to two. A sixteen-episode K-drama in standard quality fits in around ten gigabytes; a twelve-episode anime cour in about three.
On a PC
Several services offer downloads in their Windows apps too, so a laptop can carry a season as easily as a phone.
