Eoreobuteun Simjangi Nokgo Namyeon

Centuries ago, Hestia was born with incredible magic, so she was the only one powerful enough to sacrifice herself to save the world from a great evil. Now, she has been reborn into a new body and retained her magic and memories from her past life. Hestia's only goal in this life is to make her sister happy. The only problem is her sister wants to marry Yanik, an immortal who's been waiting for Hestia's return. Can Hestia keep Yanik from discovering her identity so that her sister can marry him?
(Source: Tapas)