Rengoku Hime

A hidden realm known as Rengoku lies beneath the surface world and is filled with a toxic gas called "ren." While dangerous, this gas has also introduced new potential for humanity. Artemisia, or Alto, is the first princess of Ei and possesses a body that connects to Rengoku, causing her to emit "ren" uncontrollably and harm those near her. As a result, she is confined in a dungeon, cut off from the outside world. She meets a young knight named Fog, and together they accept a royal directive. Alto aims to master the unique power of "ren" and become a "Rengokushi."