User blog comment:B214/Question & Answers 5/@comment-98.227.238.52-20150513171226/@comment-3965848-20150513173325

If fusion is possible in DxD universe then it wouldn't hard for Ddraig and Albion to fuse, opposites coming together is an interesting concept, like Kiba's Holy Demonic Sword. Like the saying goes "opposites attract",

Plus, since Issei already has the abilities of both Ddraig and Albion alone, there's really no point in it.