The second anime of Kuroshitsuji, Kuroshitsuji II, featured brand new characters including main characters Alois Trancy and Claude Faustus. The main characters of the original series, Ciel Phantomhive and Sebastian Michaelis, are still involved in the main plot, but the show isn't exactly focused on them.
Alois and Claude don't seem to appear in the Kuroshitsuji manga.
Is there any official discussion of why the second season of the anime created completely new main characters and a completely new plot?