Kurosu Ouma was the father of the main protagonist, Shu Ouma and his older sister Mana Ouma. After the death of his wife Saeko Shijou, he married Haruka.

A genius, he was the scientist who discovered Void Genome to be an inhibitor of Apocalypse Virus. Together with Shuichiro Keido, his friend and fellow scientist, he led the research about the Apocalypse Virus. However, over the years, Keido's became increasingly embittered towards Kurosu as he witnessed his colleague's success and intellect steadily eclipse his own.