Prepare a box of tissues before you read Byousoku 5 Centimeter.

Even if you are a rock, this manga has the potential to dehydrate you by exhausting you of your tears. The feels are so heavy they just can't be done proper justice in a review. Both the art and story are perfect and convey the feelings of the characters extremely well. This is a must read if you enjoy emotional dramas, romance, or if you just like to cry. The best part is that this manga also has great reread value, the feels will hit you again and again; and the tears just keep flowing.

TLDR; Read, feel, cry.