Dirt poor Jinyoung is offered the opportunity to shower to his family in riches: all he has to do is live a single year in the palace of Mark, a man cursed into the form of a great white bear. When Jinyoung discovers the curse lifts every night to change his bear companion into a passionate lover, his life seems like a dream come true—but will he be able to stay true to his bargain when his curiosity tempts him to break the rules of their relationship? Markjin Fairytale AU!

https://www.asianfanfics.com/story/view/1345687/east-of-the-sun-west-of-the-moon-romance-fairytaleau-got7-jinmark-markjin-marknior

PS : I really love fairytale :(((( because I never heard of this story before so I did search of this story and finally found it. And here the link for the one who never knew about this story hope it will help : 

https://storyberries.com/east-of-the-sun-and-west-of-the-moon/