Mastumori was Doctor Allison Mann's father, and also her main rival in cloning research. Mostly seen inside a biohazard suit with an opaque helmet, he seems to be responsible for Ampersand's surviving of the plague, due to testing of a special serum, and the plague itself. When the plague hits, he hires the ninja Toyota to retrieve Ampersand. He is revealed as Dr. Mann's father in issue #50, having also survived the plague. However, his survivor guilt and personal feelings toward the necessity of the male gender leads him to attempt a murder-suicide with Yorick. He is stopped by Allison and killed during the struggle.