Perché l'amore qualche volta ha paura - Que serais-je sans toi?, by Guillaume Musso (2009, France)

Martin, 20-ish, experiences a summer in the USA. He meets Gabrielle and it's devastatingly love. But then Martin heads back to France and, as he dates her in New York, she doesn't show up. This marks Martin's life ..until, 13 years later, a complex plot makes them meeting again in San Francisco ...and a magic step's crucial too.
Although pretty involving, the plot sometimes turns out too forced and not particularly enlightening.