User blog comment:Piyush Banerjee/Shin DxD 2 discussion/@comment-2607:FB90:4A8E:C500:80A:87B2:1048:97F3-20190609012154/@comment-38340421-20190614013029

I thougtht that super devil rank is for devil kings. Isn't that what they want to promote him to next. But are afraid of him rejecting it because it would be a title and the only one Issei cares about is harem king. Plus i think ultimate class devil is reserved for lucifer tier power devils. Hence those special devil names were turned into titles for the top tier devils.