Board Thread:Wiki Discussions/@comment-4704473-20140416230513/@comment-4912646-20140425163130

Seelentau wrote: Fifth mask? Now that I'd like to see, if it's possible.

The fifth mask is shown in chapter 336, when Kakuzu is explaining how he steals hearts. It was omitted in the anime version of the scene. Maybe he had a different set of masks in the past?