Reaching his limit due to daily work, the corporate slave Enami Shuusuke collapses on the station platform one day. In that moment, memories of his childhood friend, Yorumiya Hina, who died in an accident, flash before his eyes.
"I'm sorry, I couldn't save you then."
As Shuusuke falls into a deep sleep bearing regret, he finds himself time-leaping back 10 years!
