For this specific movie, it doesn't seem like there's an official English sub ever made. There's also doesn't seem to be any fan-made that I can find.
Generally, I think https://www.opensubtitles.org is best.
If you're ever worried of something like this happening you should archive their Instagram, Instaloader is a great way to do it, I've archived plenty of accounts I like.
VPN services. You can select a server in Korea or almost any country, and it becomes your device's location.
And unless you want your phone/laptop to be tracked and you don't care, pay for a decent VPN like NordVPN.
https://play.google.com/store/apps/details?id=kr.co.watch.bnnlv.android
https://play.google.com/store/apps/details?id=kr.co.ppaptv.android.air
Apparently those two that I have mention are no more... Now there is appletv and bananatv