Not too old movie, with a similar plot to Love and anarchy netflix series.

Searching a movie where a boy and a girl knows each other from childhood. They start to play a wierd game: who has this box (maybe a lunchbox?) must do the thing who the other asks. After completition they change rolls.In the movie they grow up but they continue to play this game. On the end one of them died becouse of this wierd game. (maybe)
The plot is very similar to “Love and anarchy” netflix series. It was a french movie (maybe).