Goodbye, Sadon!

In high school, he thought she was a bully and she thought he was a huge jerk. Years later, Han-Eol and Da-Hae meet again... because their siblings are getting married! But tragedy strikes the newlyweds and their loved ones are left to wonder how they could have saved them. Han-Eol and Da-Hae awake to find themselves in high school again—and their siblings are alive! With only each other and a diary to rely on, can they weave a new destiny for their siblings? Or will fate unravel all the same?
(Source: Tapas, edited)