Death-ko

A small demon monster girl Leo can find in the second playthrough. She carries a scythe and is obsessed with killing. Her hobby is killing. Her favorite thing is killing. She hates not killing. She lives to kill.

During sex she refuses to allow Leo to use MX potions that prevent his semen from being poison so he's forced to kill her with no hope of rebirth. However since she's a monster girl of death she won't die. This means she never becomes pregnant and has no child version.