"Promise we will remember each other forever and ever?"

                                          "Promise. I promise I'll stay with you forever...in here" he pointed to her heart.

 Hye Na and Onew/ Jinki were best friends in the orphange for 2 years. And of course, their bond was strong. They promised each other to keep one another in their hearts, forever. They were happy. Until Onew/Jinki was adopted.

Years Later, Hye Na was adopted too. Expect the unexpected. They met once again. And the situation wasn't as simple.....