In 2001, Demy received the best actor award at the Festival de Paris for Quand on sera grand directed by Renaud Cohen.

In 2009, he also starred in André Téchiné's La Fille du RER and in the television drama Mes chères études, directed by Emmanuelle Bercot and dealing with a students' prostitution.

In 2011, Demy appeared in Céline Sciamma's Tomboy and was cast as the lead in the romantic comedy L'Art de séduire by Guy Mazarguil.

Since 2012 Demy has continued to act in films such as Les Conquerants by Xabi Molia or My LIttle One by Frédéric Choffat and Julie Gilbert.

The show was created by Anne Berest and Fabrice Gobert ("Les revenants") and was broadcast on Arte, where it gathered 2 million views, and available on Netflix for the international audience.