User blog comment:B214/Question and Answers 3/@comment-62.178.18.58-20140813224147/@comment-62.178.18.58-20140818171236

Sorry for the late answer, was busy the last week.

 I hope you realize that the term legal wife means that you can only marry one woman LEGALLY. This was basically my question: “Is it possible to marry more than one person?” with which I meant:” Does the underworld legal system recognize the existence of more than one wife simultaneously?” Of course you can call everyone and their mothers your “wife” but this doesn’t give them the rights of the “legal wife”.

 Given that there is no evidence to the contrary I will assume that like in the real world, in the fictional underworld of DxD you can only marry one wife legally but the existence of mistresses (even if you call them your “wives”) is just socially accepted.