Neco-Arc is a member of the Neco Spirit race, originating from the Great Cat's Village.]
She became Ms. Ciel's student, constantly acting up in retaliation for having such little screen time and wishing people to think she is smart. She is referred to as the "work of Kischur Zelretch Schweinorg" according to Aoko Aozaki, suggesting she was brought from another world, but it's also said that there is a "certain urban legend" telling of six Neco-Arcs and one that exceeds them 