1 + 1 = . . . 3?

  They say that love is blind and in this world, it certainly is.  

You shouldn't make promises you can't keep. At least not to wrong people, like Do Kyungsoo. Otherwise, you will have to pay, because when Kyungsoo sets his eyes on something, it's his till death... Or even longer?

People tend to make mistakes - bigger or smaller ones. It's inevitable in life. But every mistake you make, sometimes, brings very painful consequences.

Kim Junmyeon is tired. He's lived for thousands of years already, and he's sick of life. He's visited tons of places, seen billions people and all of this is dull for him. Colorless, boring, and lifeless. He had everything, but nothing lasts forever. When one day, he meets a young girl with a cold, expressionless face, he became interested for the first time in so long. And... it

Of all people... why he had to fall for Mingyu? 

How can I live in this world, when my world left me?