Walking home from work one night, Shuuichirou Kudou encounters a child-like being with wings trapped on a tree branch. After he saves the creature, they introduce themselves as Kohaku, an angel from Heaven. Skeptical of the supernatural, Shuuichirou ignores Kohaku and goes back home, dismissing it as a dream.

The next day, Shuuichirou finds Kohaku in his garden, who has now taken on their true form. They tell him that, for his kindness, they want to grant him any wish. However, Shuuichirou is content with what he has and declines. Kohaku decides that, instead of doing nothing, they will stay with their savior until he desires something only they can deliver.

Although Kohaku becomes accustomed to their homely life with Shuuichirou, they cannot remain on Earth for long due to being tormented by Kouryuu—a mischievous devil—and his sidekicks. In addition, Kohaku is on borrowed time to find the missing archangel Hisui and must hurry before they are both banished from Heaven forever.