Noooooooooo...
Well, is quite possible Arimura just lend some help to a drunkard and let Kusanagi stay in her place. The fact she was wearing only a bra is still worrisome.
But even tho Kusanagi had her share of girlfriends in the past it would still be frustrating if she gets involved with Arimura after meeting Hina. IF by any chance that happens we all know who would be there to confort Hina.
Seriously rather the series dont get this complicated.