User blog comment:B214/High School DxD DX.4 discussion/@comment-39.51.176.224-20170906050225/@comment-1359322-20171019122605

And what makes you think Grayfia isn't God-class. Serafall, Falbium and Grayfia are already stronger than the original Maou. Not to mention the thing regarding God-class > Maou-class is pretty much just fan speculation. Ishibumi himself has never outright said that God-class is stronger than Maou-class.