Ich und Du

Lorenzo is a quirky 14-year-old loner. He plans to fulfill his teenage dream of happiness by hiding out in his apartment building’s abandoned cellar. To escape his overwrought parents, Lorenzo will tell them that he is going away on a ski trip with school friends. For an entire week, he will finally be able to avoid all conflicts and pressures to be a "normal" teenager.
He plans to live in perfect isolation with his horror and fantasy books. But an unexpected visit from his worldly older half-sister Olivia changes everything. Their emotional time together will inspire Lorenzo to come to terms with the challenge of casting aside his disguise of troubled youth and prepare to soon be thrown into the chaotic game of adult life. (http://www.festival-cannes.fr/en/archives/ficheFilm/id/11257217.html)