A character from Houseki no Kuni, a personification of the red, mercury-containing mineral cinnabar. Shinsha is the only Gem referred to by the Japanese name of the mineral, albeit in katakana, rather than a western name.
Small "clouds" of native mercury appear to float around Shinsha at all times. In the same way that mercury is harmful to human beings (due to its toxicity) and destructive to metals such as aluminum (due to forming amalgams that compromise their strength), Shinsha's very presence is hazardous to their fellow Gems. As a result, they have been forced to live a mostly solitary existence, well removed from the "school" where the rest of the Gems live.