User blog comment:Crimson and Darkness/Volume 25 discussion blog/@comment-2208155-20180520143001/@comment-30924344-20180520153632

I didn't though. Great Red = True Dragon. He mentions Issei becoming the True Oppai Dragon. Fifth arc title refers to Issei as the "True Dragon of Kuoh Academy" (it's not Dragon(s)). Really sounds like he's calling Issei a breast version of Great Red.