Time is free,

but it's priceless.

You can't own it,

but you can use it.

You can't keep it,

but you can spend it.

Once you've lost it

You can never get it back

Yuri, the nerd girl who didn't believe in  friendship. Everybody wanted to bully her even her elder sister, Jiyeon. Jiyeon, the pretty girl, she hate her sister because she thinks that Yuri made her felt embarassing. Jiyeon don't want a sister who was a nerd. One day, Jiyeon fall in love with a guy, Kim Jongin. Kim jongin, the kingka in Sm campus who always bullied Yuri until he fall in love with Yuri's sister. Yuri always felt lonely until she met a guy, Do Kyungsoo who always at her side. A few months ago, something got wrong. Everthing went wrong....

All because of a clock