User blog comment:CandyGoreCat/About "Two Sided Tenma"/@comment-29899082-20170117164724

It could be that or it may be a way to describe how they have both angel and demon characteristics rather than being a 'hybrid' with an angel parent and demon parent, instead they were created with as both like how a hermaphrodite is born with both organs naturally rather than having one or another.

Or it could just mean they're a hermaphrodite.