I'm just impressed how the author managed to make things progress fast, and yet still feels simple and naturally. Everyone acted stupid, but things didn't feel off still.
Also, I blame Fujiwara cuz for someone so "righteous" he really made the effort to seduce the girl. And that was after already rejecting her and making it clear "it's impossible".
I didn't expect much from Hitsuji, frankly because her feelings never went away. I'm a bit glad she tried to push Fujiwara away, but yeah, it was impossible to let go of her feelings from the start so they should have broken up the moment Fujiwara started seducing her, or simply should have never participated in the rebound strategy in the first place.