She let him go because she knew she could never have him.

It started with a simple smile and ended with a warm hello.

Soon, he's going to leave you. Soon, you'll be left alone. But there is one thing he wanted you to do, to smile.

  Jong In fell in love with Kyungsoo but Kyungsoo isn't sure of his feelings. He had come up to a decision, that both of them would get hurt.   Both of their lives would change.   Both of their hopes would differ.   Both of their hearts would crash.   And both of their souls would be rip.        

How does love tastes? Is it as sweet as honey or as bitter as your desire?  

For the last clue...   "Go to my room...   Face the mirror...   There you'll find my most precious treasure."