Agnes and Pierre Anthon
The biggest way in which Pierre Anthon illuminates Agnes's character and she illuminates his is through their arguments about meaning. Agnes thinks it exists (or is very invested in pretending to); Pierre Anthon thinks it doesn't. They have philosophical battles in which she yells up from the sidewalk and he yells down from the tree. When Pierre Anthon walks out the door, Agnes is tempted to follow, but she chooses the opposite path: she's going to keep wearing her mask, while he takes his off. Her covered face makes his bare one stand out all the more.