On his way back from work, Shuuichirou Kudou comes across a winged, child-like being stuck on a tree branch. Upon rescuing this mysterious creature, named Kohaku, it reveals itself as an angel from Heaven. Despite Shuuichirou's doubts about the supernatural, he saves Kohaku and returns home, brushing off the encounter as a mere dream. To his surprise, the following day, Kohaku appears in his garden in its true angelic form. Grateful for Shuuichirou's kindness, Kohaku offers to grant him a wish, but Shuuichirou, content with his life, politely declines. Instead, Kohaku decides to stay by Shuuichirou's side until the day comes when he needs their unique powers. As they grow accustomed to their shared routine, their peaceful coexistence is threatened by Kouryuu, a mischievous devil, and his followers who torment Kohaku. Time ticks away as Kohaku races against the clock to find the missing archangel Hisui, knowing that their time on Earth is limited before they face expulsion from Heaven.