Same story from same novel. One is a 58 episodes drama and one is a movie. Both drama and movie have amazing cast
Similarities: Female lead will forget everything due to the betrayal of the male lead. The female lead will love the male lead after forgetting everything but will be the most vengeful once their memory returns.
Differences: Once Upon A Time is a film while Good Bye My Princess is a drama. The male lead of Once Upon A Time did not truly betray the female lead while the male lead of Good Bye My Princess truly betrayed the female lead.
Differences: Once Upon A Time is a film while Good Bye My Princess is a drama. The male lead of Once Upon A Time did not truly betray the female lead while the male lead of Good Bye My Princess truly betrayed the female lead.