Yin and Yang are twin sisters, nicknamed by their adoptive father. Of the two sisters, Yang was always the more caring, the more loving twin.   Yang never knew her biological mother, as she died when Yang was young. When she was a slightly older child, her father was assinated by a killer named Apple Blossom. Boss Kazazumi saw potential in the twins and adopted them as his own.     In adulthood, after Agent Succubus was captured and brought into the Kazazumi Family torture area, Yang fell in love with her.  The two planned to escape together, to live a life of peace, until Yang’s twin sister Yin murdered Agent Succubus through tickle torture.   Yang vowed never to forgive her sister and returned to take over the Kazazumi Crime family syndicate after her adoptive father’s death.