You are aware that this is the same character so it's not lesbian sex its masturbation :O ... um anyway the condom could be for a guy off screen that they're gringing on each other for in order to turn on and we're seeing in his pov. 3 ways sometimes go like that.
Well there's actually more then two. The strip of them is coming out from Kotone's bag, and considering how they're looking towards the same direction and not at each other it's obviously for an off screen guy.
True. To clarify: In the original H-manga, one of these is actually Blue's Ditto transformed into its trainer, so two Blues can have a threesome with Red.