Once upon a time it was a pair of brothers, Dalsun and Haesik, they lived with their mother who had been widowed. Their home was deep in a mountain valley. To survive with their children, the mother worked doing housework in the houses of neighboring villages.

Once the mother didn't came back.

Dalsun and Haesik were so worried about her and their lives, what would happen to them without their beloved mother? How would they survive? . A tiger, that was their mother's assasin, went after them because it was so hungry even after had eaten the woman, so the children full of panic prayed to the God of the Sky.

"Oh God, please save us" 

It fell a rope from the sky and the children climbed on it through the clouds, and they had become in God and Godess. 

Haenim, the sun that lights the day and Dalnim the moon that lights up the night.

Dalsun is tired, she doesn't want to be the Godess of the Moon anymore. She's tired of watching humans making their lives when she can't do the same.
It's tired of seing how them cry, laugh, play, argue and love. She wants to feel and live like them too.

So she flees from heaven when the sun isn't there to see her. Careful not to wake the sky, she falls to earth and takes possession of a human body to fulfill her wish.

The chosen body belongs to a boy not a girl, and he had committed suicide.