Young people who meet the definition of "Hikikomori" have come to be seen in France since around 2008. However, simply "fitting the definition" does not necessarily mean that they are the same as "Hikikomori" in Japan. Rather, it is important to ask what kind of young people "fit the definition of Hikikomori in France" and what kind of pathology they have. With these questions, our Japanese-French joint research team comprising specialists in various fields conducted a survey of "Hikikomori" in French youth, with support from a Grant-in-Aid for Scientific Research B (overseas research), and started a comparative joint study on "Hikikomori" in Japan and "Hikikomori" in France. In that study it was found that whereas one aspect of "Hikikomori" in Japan is described by the word deraillement (coming off the "rails"), "Hikikomori" in France is a state closer to dropping out and is accompanied by a type of "sense of insufficiency". This "sense of insufficiency" is above all related to something in the society and culture of France, and an investigation of how it is linked to "Hikikomori" is an issue for the future.