One night, while walking home from work, Shuuichirou Kudou comes across a child-like, winged creature trapped on a tree branch. After rescuing the being, it introduces itself as Kohaku, an angel from Heaven. Skeptical of the supernatural, Shuuichirou ignores Kohaku and returns home, dismissing the encounter as a dream. The following day, Shuuichirou discovers Kohaku in his garden, having now assumed their true form. Kohaku explains that, in gratitude for his kindness, they wish to grant him any desire. However, Shuuichirou is satisfied with his current life and declines. Kohaku decides that, rather than doing nothing, they will remain with their savior until he asks for something only they can provide. Although Kohaku grows accustomed to their domestic life with Shuuichirou, they cannot stay on Earth for long because they are tormented by Kouryuu—a mischievous devil—and his sidekicks. Furthermore, Kohaku is on borrowed time to locate the missing archangel Hisui and must hurry before both are banished from Heaven forever.