An old mobile phone opens a mysterious time channel that allows Ye You Ning in the year 2019, to communicate with Xia Wen Xi in the year 2006.

The probability of them meeting was one in a billion. In a parallel time and space, the cold and unapproachable top student Ye Youning encounters the bright and sunny Xia Wenxi. Through an unexpected opportunity, Ye Youning (Patrick Shih) from the future connects with Xia Wenxi (Amy Chen) from the year 2006. Their encounter leads to a sweet romance and a chance to relive high school, to meet old friends again and to experience the taste of first love.—ChineseDrama.Info

In the year 2019, eminent physicist Ye You Ning travels back to his hometown in China from abroad after many years to take care of his ailing grandfather. However, after a thunderstorm, he finds himself transported back to his school days as a student in the year 2006. He discovers that the secret of his time travel lies in the mobile phone of Xia Wen Xi, his optimistic and sunny deskmate.—Amazon Prime Video

In the year 2019, eminent physicist Ye You Ning travels back to his hometown in China from abroad after many years to take care of his ailing grandfather. However, after a thunderstorm, he finds himself transported back to his school days as a student in the year 2006. He discovers that the secret of his time travel lies in the mobile phone of Xia Wen Xi, his optimistic and sunny deskmate. As he attempts to go back to his original timeline by communicating with Xia Wen Xi through the phone and manipulating events in the past, he gets to relive his life in various situations, goes through regrets, and gets to know the gravity of the choices he had made and the true worth of the people he met, including Xia Wen Xi and his old classmates whom he had failed to cherish.—MyDramaList