User blog comment:B214/Question and Answers 4/@comment-74.110.108.150-20141204134423/@comment-1359322-20141205130510

"“Michael-sama and the other Seraphs are at the Sixth Heaven. That’s where the main headquarter of Heaven is based at. Well, the lowest ranking Angels including myself mainly comes here—the frontline base of First Heaven.”"

The sixth floor belongs to the Seraphs.