Invaders of the Rokujouma!? Volume 6

Lately, Koutarou has been growing more and more suspicious of Kiriha. Claiming that she's come to invade the surface is one thing, but what on earth is she doing helping the neighborhood association clean up the city? Is this all part of some nefarious plan? Or is there something else going on? When Koutarou works up the nerve to confront her about it, she responds by... asking him on a date?!