From NetComics:
Shinhye loves lying under the night sky with her father, listening to his tales of the constellations. And she dreams of a life among the stars. Little does she know that the stars may come down to her instead. Her journey begins when the department of science asks her family to host Sarah, a foreign girl with a unique talent. But, strange men are interested in Sarah and Shinhye doesn't know why. Unbeknownst to Shinhye, her every dream--and nightmare--is about to come true.

[From NetComics]:

Ordinary high school girl Jina discovers that she is heir to a terrible legacy handed down from her family's sinister history. Long ago, her ancestors killed a magical serpent known as an Imugi, believing that it would bring them good luck. Unfortunately, the creature cursed them as it died, decreeing that one family member of each generation for that day forth will be killed by two people closely acquainted with that person. One of Jina's relatives has been murdered without fail in every generation, and now, Jina has been informed that she will be next to die.

[From JanimeS]:

Se Young was a high school girl who has peaceful days until recently a worry begin to bother her. She had a childhood friend, apparently a boy, who also goes to the same school. His name is Heun Uoo. (Note : Their last names are not discussed here). Being a childhood friend, Heun Uoo does not have a feeling for Se Young, at least not as a female. However, Heun Uoo does care of Se Young in a way that Se Young is not satisfied of.