Ten thousand years of darkness have passed since a catastrophic tsunami drowned the world above. Deep underground, civilization survives in fragmented pockets, waiting for someone foolish or brave enough to seek the surface again. Mokugyo is an unlikely hero: a fish with plants sprouting from his back, paired with Toriiruka, a creature whose endless chatter masks genuine wisdom. When a solitary, prickly creature named Harry and Yona, a young woman carrying the genetic memory of an ancient civilization, find each other in the depths, something shifts. Yona's bloodline holds the secret to restoring what was lost, but reaching the surface means crossing treacherous underground territories and confronting the reason the world flooded in the first place. What begins as a survival journey becomes something stranger. These mismatched companions must uncover the truth about Luna, the giants who once ruled and granted humanity its greatest gift, and why their world collapsed. The path upward promises answers, though not all revelations lead toward hope. Together, they push toward a light they've never seen.