Shinigami to Chocolate Parfait(2007)

Shinigami to Chocolate Parfait

Jinna Amakura was a typical, if not a bit stingy, high school boy. Typical, that is, until he died. Or... at least he was supposed to die, but he didn't. Jinna is now considered by the powers that be as a "Soul Irregular".
Enter Nagi. Nagi is a Grim Reaper on her first job - to kill Jinna and return his soul to the proper cycle of life and death. If she fails, she will be turned into her favorite dessert and eaten by the head of the Angels of Death. Not only does her job start off as worse as it possibly could, but Nagi and Jinna form an almost friendly, if not unusual relationship... just wait till her boss finds out... (Source: Manga-Heaven)

Volume 1 contains an extra side story chapter.