Board Thread:Manga Discussion/@comment-4828844-20170703123353/@comment-31525652-20170703124846

Someone on reddit speculated the two faces are of the last two women we saw enter his hotel room. Not the ones we saw first since they look nothing like the faces of the Nen beast, but those we saw in the last page of Chapter 345.

Also I think the theme of his Nen beast is his "adoration" of women. I mean look at those high heels, and coughsteel nipplescough. It makes perfect sense for the second head to be of a woman as well.