I mean, I guess this is about as definitive an ending as they can get away with without raising the age rating.
Cause yeah, last time Kaede snapped, the other two were genuinely scared for their chastity. This time, Kaede is at least somewhat capable of explaining what she wants, even if I doubt anything will be stopping her.
Meanwhile despite big sis getting all flustered from flirting with Chiaki, we all know she's a degenerate voyeur who is more than willing to throw Chiaki under the bus to save her own skin.
So you have a flustered Chiaki who just got confessed to by her first love and doesn't know what is going on, and a very horny and upset Kaede. Yeah, the only real question at this point is exactly how consentual this sex is on Chiaki's part.