After being stabbed in the chest by his mother, Kyosuke Date returns from the dead to find out he has a twin sister, Runa and the ability to transform in the mutant known as the SoulTaker. As he seeks out his sister, he is being pursued by the strange mutant doctors and nurses of the Hospital, led by his own father, Richard Vincent, as well as the evil Kirihara corporation, led by Yui Kirihara, who is also tracking down Runa for their own malevolent purposes. Assisting him along the way are the mysterious Shiro Mibu and the nurse mutant girl Komugi Nakahara, who betrayed the Hospital out of love for Kyousuke.