Orange 2015 (Japan) is Japan drama premiere on Dec 12, 2015
During the spring of her 16th year Takamiya Naho receives a letter from her future self. Upon reading the initial page of the letter, her class was introduced to a transfer student from Tokyo named Naruse Kakeru. The letter she realized was an account of the things her future self had experienced and regret the most. Frightened, she tries to avoid reading further, but as her interests towards Kakeru bloom Naho eventually decides to encourage him. Naho, together with the help of her friends, Suwa, Chino, Hagita, and Azusa do their best to avoid having the same regrets their future self had, and heals Kakeru from his desolation and self blame.
(Source: Written by MyDramaList)