if that was the case, then why use the password, or why Julia justifies herself with MC, when she can fuck with Connell without MC seeing, in the betrayal route, Julia fucks with Connell in the bunkalof while MC and Jasmine are hidden, if Jasmine doesn't stop MC, it would inevitably happen, so I also predict some tragic endings.
The safe word is suggested by Cornell, who knows full well that the MC knows his character. It's there to control Cornell, not Julia.
First, if corruption=0, it's just a mild romantic comedy. Nothing happens, still that's kind of funny in its own way, as things keep happening that are pretty comical.
If corruption is high. Julia finds out about the MC's fantasy. She discovers that MC is enjoying it, either by confessing it to her directly or indirectly by not saying it when MC is supposed to say the safe word.
Here again, the paths diverge. If the MC doesn't suggest that she and Cornell sleep together, then all she can do is give Cornell a blowjob. Since Julia has done something very provocative with the MC's permission, such as taking a nude photo in front of the MC, she might think that this is enough to not cross the line.
Julia is only sleeping with Cornell because MC gave her permission once, and she continues to do so because MC has confirmed to her that he enjoyed the situation as well.
As long as MC isn't cheating, Julia is (relatively) faithful to him or to their shared fantasy.
A tragic ending would be if the MC cheats or Julia gets pregnant, but both of these things happen because of the MC's choices. If the MC controls the situation correctly, it will end happily.
ps) She has no idea that he's watching her on a hidden camera or under their bed. She simply assumes that MC is enjoying the fact that she had sex with Cornell, and that he's also enjoying hearing about her experience.