What about not shutting down Yumi's advances from the start?
I explained it earlier!
With both the producer and Shinobu, one key detail was shown when it comes to Sakura.
So far, she'll feel good being touched by anyone. Even if it isn't Shinobu.
During the foreplay with both Producer and Shinobu (mainly when she was being touched) she'd mentally note how her thoughts were being mixed and confused. How she was becoming hazy and how her mind was going blank. Then she cums and, as she thought, her mind went blank. She becomes weaker the more she was pleasured.
That's the flaw about Sakura when it comes to it. Despite the brief moments of telling Yuma to stop or wait a sec, he didn't. He kept touching her. We don't see her thought process here but can deduce from her two prior scenes that she was becoming hazy. Confused. Her mind was going blank and on top of that she was an emotional mess from thinking. shinobu cheated on her.
Once Yuma made her cum, her mind simply went blank. For a brief moment she began to collect herself even if she wasn't fighting back when being moved to the bed and stripped. But the moment Yuma thrusted into her, the pleasure overrode her thoughts and she went blank again. No doubt just giving in to the pleasure. Even if she was like a doll. Because unlike Shinobu, with Yuma she just layed there and took it without saying anything. The only effort she put in was the kiss he gave her while being fucked.