Title: Half and Half,
Author: Seo Kouji

Genre: shounen, romance, supernatural, tragedy

Total Volumes: 1 (oneshot)

Kenn's comment: Good things come in small packages. From the same author of Kimi no Iru Machi, and Suzuka. A good read.

Summary from MangaUpdates:
Shinichi Nagakawa and Yuuki Sanada are both involved in an accident and die together. But they're given a chance to live again. God lets them live for seven more days. But the catch is that after the time limit, one of them must die again.

There's more. God decrees that their lives will be shared, including emotions (guilt) and physical sensations (pain). They are told not to leave the other's side, else both of them die. What will happen during those seven days?...