User blog comment:B214/Volume 21 info & spoilers/@comment-26865730-20160409182012/@comment-26865730-20160411005437

Yeah, it was #3 War Acheivement that I thought would do it for him. But then again, becoming a High Class Devil is a dream that 99% of Devils could never aspire to. So even at this level, Issei will have come a long way.