The game follows main protagonist Kor Meteor after he discovers a woman named Kohaku Hearts and her brother Hisui near his home town. When Kohaku is attacked by a mysterious antagonist named Incarose and infected with a monster called a Zerom, Kor attempts to cure her using his soma, an ancient weapon designed to fight Zerom. In the process, he ends up shattering Kohaku's spiria, the essence of her heart and emotions, and scattering the pieces across the world. Together with Hisui, Kor sets off with Kohaku on a quest to restore her spiria. The game's central theme is Kokoro to deau RPG (心と出会うRPG?, lit. "A Meeting Between Hearts RPG"). ForHearts R, extra story scenes were created and the genre name was altered to Aratana kokoro to deau RPG (新たな心と出会うRPG?, lit. "A Meeting Between New Hearts RPG").