He is a short, slender, balding French man. He is manifested after camera that Balubal Razon is recovered and given to Steven. He is a physicist specializing in temporal mechanics, causality, and quantum theories. Steven manifests him after reading a number of books related to the topic.
J.C. seems to like him, though the friendliness is not really reciprocated. This may be because, after Arnaud makes a speculation about the nature of the aspects and how they can remember having past lives, he takes it to mean he is an Interdimensional Time Ranger.