Future Diary

One day, Erick knightwalker receives a journal written to himself from ten years in the future. As Erick reads on, the pages recite the exact events of the day, including the new student in his class named Samantha scarlet
The Erick from ten years later repeatedly telling his past self to watch over Samantha closely.
What's more shocking is that he discovers that ten years later, Samantha will no longer be with him.