Mahoraba/WMG

Natsume Konno is the dominant personality in Kozue Aoba

 * Think about it this way: notice how whenever the other personalities are shown at once, especially during Kozue's breakdown, it's always Natsume who acts first. She's the one who, despite all the other personalities there, speaks to him during their final scene in chapter 60. For all we know, she could be the "ruling" personality who protects the others--even when Kozue's normal self is out. Note her magic and how she manages to listen in on everything.