The entire 3rd volume is nothing more than some form of tentacle rape to the various girls. I think every chapter one or the other is getting hosed. Well the start of the volume Ayana is getting molested by a bunch of guys.
Volume 4 is the when the action happens after them getting jealous from the new cat girl that appeared in volume 3 so they invade his bath. Also still plenty of tentacle rape. The mangaka is seriously fucked in the head with that shit.
Skipped volume 5 fuck all that tentacle shit.
Volume 6 was a flashback volume that got a little dark with some flashbacks. Ending was ambiguous with the 4 girls as most of these type are.