Subject-018, or "Nihachu" as she calls herself, is a Mutant Hybrid of sorts. Appearance wise, she seems to look like a cross between a human and an axolotl. Genetically speaking, she has both human and amphibian traits. Her origins are currently unknown, and she herself doesn't recall anything from her childhood, as her only memories involves living her whole life in the swamplands of Japan where she was found, treated nicely by the locals, who gave her the name "Nihachu".