Board Thread:General Discussion/@comment-4680574-20140324180244/@comment-12776-20140726084725

Simple, it doesn't count as "cheating" if there's no bond between you two, it's just one night affair. Does a prostitute cheat on you when she has sex with another customer?

And so, if mamono doesn't consider you to be her husband (or big bro, or uncle, or master, blah blah blah), then it isn't cheating. The only two mamono that state to have more than one husband are Queen Slime and Charybdis, but neither hide other guys from another. Plus, Queen Slime actually has many bodies that it hardly count.