Give to the Heart  Vol 3,4,5,6 Manga Books  by Wann (Author, Artist)
In the far-off distant future, the Earth suffers a cataclysm that destroys modern civilization. Over centuries, human survivors regroup and organize into primitive cities. Three godlike beings arise and oversee the well-being of the world. Lord Ganok rules all waters. Nations prosper ― or starve ― on his whim. He nourishes farmlands with rainfall or blights entire realms with drought. He can unleash violent storms that level entire cities. Yet, despite all his awe-inspiring abilities, the Water King can't win the heart of a simple human woman named Sooyi. Lord Ganok quickly learns that the human heart contains more intense storms than he could ever hope to create. Furthermore, Sooyi seeks out a power of her own in order to fulfill an old vendetta...the power to slay the Water King once and for all!