Inspired by the manga and anime adaptation "Orange" which you should totally check out first: When Kim Taehyung receives a letter one morning from himself 10 years in the future, he thinks it could be nothing but a joke. However, as the letter begins to match up to Taehyung's reality, right up to meeting the new and mysterious Jeon Jungkook, he starts to wonder if it could be the truth...and if it will encourage him to change the future.

- the backstory/au of what Taehyung wrote about in the song "4 O'Clock"