User blog comment:DeathGodPrayer/Talk About What You Want!/@comment-4917660-20120529045854/@comment-61.4.110.238-20120529061434

The reason why the anime can finish before the manga is because the original story is at the light novels. Also the manga went into a hiatus shortly after being published due to not receiving good response. They continued it last year after they promoted the series for anime.