Momo is a shinigami (a Grim Reaper), the messenger of death. Unlike the scary dark cloaked man holding a sickle, she is draped in gleaming white—her gown, sickle, hair and all. Accompanied by a black cat named Daniel, Momo takes up a mission to convey human souls to the Great Beyond. She appears before dying people and relieves them from their mortal fears, but she also comforts those who suffer the anguish of losing loved ones in tragedies.

Seven Seas Entertainment published the first two novels in English from March 18, 2008 to July 8, 2008, but the license was suspended due to low sales.