The manga recently became available on Amazon Kindle in Japan.
"Yari is a sixteen-year-old girl who goes for Taiwan for the first time with her friend. In that trip she meets a boy named Li Kemin, a manga editor. They fall in love but they have the time, the language and the distance as a barrier to their love. It's a romantic story in a girl perspective that talks about all the trouble in the long distance relationship and what it takes to beat it."
Love Letter like many of Yazawa's early works is only one volume long. The first chapter is titled, "One Hour of Difference."