It occurred to me after watching this film that the strange dance that Leo and Yoan do through each others lives, as well as their strong physical resemblance (Leo looks Yoan with his age doubled) that this narrative is a meeting of the central character with his younger self. Leo is very interested in Yoan, while the latter seems to utterly hate his older self just as much as he enjoys flaunting his bad choices and desire for all the things that Leo has thrown away--i.e. his relationship with Marie as well as an affair with her father. Ultimately this ends for Leo when his younger self manages to steal from him the thing he loves the most--his own child.
Review of Staying Vertical
