Soraoto

From Midnight Scans:

"Heaven" is a company. The job of the "Messenger of Death" is to deliver the souls of the dead to heaven. The Messengers of Death are ranked according to ability. Uka, a "Rank C" dropout, is normally an average, easy-going high school girl. One day, she is teamed up with Tsumugi, one of the "Rank A" arrogant elite!