This story is about the two Im and Kwon siblings, Yoona and Yuri. Their father, an astronomer and philosopher, always told his daughters about the wonders of space. His dream was to solve the mysteries of time and space, but before he could complete his work, he passed away, leaving his two young daughters alone in the world. Yuri’s mother ran away when Yuri was only three years old, and Yoona was adopted by Mr. Kwon at the age of five; the only one left to take care of the two of them was their late father’s best friend, Mrs. Jung, who herself also had two daughters.  

The two sisters didn’t know about their father's theory of time and space, but when they had to clean out the rest of their house, they found his papers with an incomplete theory written. As of that moment Yoona and Yuri promised each other that they would complete his theory and maybe eventually prove it - but of course with a bit of help from Mrs. Jung’s daughters and possibly some others too.