User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-3965848-20150524093458/@comment-24502975-20150526140416

It's the same situation as Koneko & Kuroka, so who really cares? It would be weird but not incest in the normal way people think of it (although legally it would be, assuming the Underworld doesn't have different laws on that as well).