Orange

In the Spring she was 16, Takemiya Naho receives a strange, but detailed letter from herself, ten years in the future. At first she thinks the letter is a prank, but then the things written in the letter actually happen, including the new transfer student that sits next to her in class, Naruse Kakeru. The letter reads just like her diary entries, down to the same characters. It is not till two weeks later, when Kakeru shows back up at school, that Naho finishes the letter...

(Source: Kissmanga)