The series is set in a fictional galaxy comprising countless moons that are beset by an enigmatic black miasma that destroys everything in its path. These moons are protected by children called Moonflowers, who use their emotional states to activate magical "treasures" that are supplied by an infantile being named Little Dreamer; the treasures can then be planted to grow trees with the power to ward off the miasma. The first episode depicts the titular character, Hanazuki, being born on one particular moon that is inhabited by several denizens, including colorful rabbit-like creatures called Hemkas who each represent a different emotion that Hanazuki reflects. Several episodes focus on Hanazuki's escapades with the Hemkas as she learns about her responsibilities and emotional states, ending with her growing a Treasure Tree that corresponds with her mood in that episode. Later in the series, Hanazuki encounters a fellow Moonflower named Kiazuki, who has failed to fulfill her duty of ...