User blog comment:B214/High School DxD EX/@comment-178.237.101.5-20151130122815/@comment-26821288-20151201151218

If I remember correctly. Demons are aging, but not, at the same time and by that, I mean: They kind of age, but they can change their appearance to the age they want, like what happened when accidently (bad English. Sorry) Rias and Asia changed their appearance to children, although, this might be unrelated, I don't really remember.

Anyway, what I try to say is, that Issei may have an older appearance, and he may have the same appearance, or even younger.