On the official H.C. Andersen Award webpage we find the following explanation:
The purpose of the award is to pay tribute to Hans Christian Andersen’s influence on authors all over the world by choosing recipients whose work can be attached to Hans Christian Andersen’s name and life’s work – for instance through genre-based likenesses or artistic storytelling qualities. The chosen authors must, as it has been expressed, be at swan level with Hans Christian Andersen.
According to the article on Yahoo News, the jury honored Murakami for his "bold mix of classic narrative, pop culture, Japanese tradition, dreamlike realism and philosophical debate." The award ceremony will take place in October 2016 in Odense, Andersen's hometown.
photograph from: http://www.detkvindeligelitteraturselskab.dk/murakami-mette-holm/