「日本鬼子」(Japan-devils) is a Chinese racial slur for the Japanese.
Leave it to the Japanese to take the insult and make fun of it by turning it into a もえ (cartoon character representing something).
That sequence of Chinese characters can be pronounced several ways in Japanese, including “Hinomoto Oniko” which sounds like a woman’s name. …
Thus, the racial slur has been owned and turned into a cartoon of a warrior woman with demon horns.
Only in Japan.
China Hush has an article on this.