Actually, it'd be really handy for me if Sophia bumped into Johnathan now, interrupting them before the explosion. As Sayuri perceives it, he's pretty much demonstrated that any attempt at cooperation or deal-making on her part only earns her more hostility and increased demands ("prove your story" "apologize"). Having someone else show up would be a good reason for Sayuri to withdraw instead of escalating her threats or attacking. Tactically, if a negotiated solution is impossible, it would make sense for Sayuri to take the initiative and attack first (since she doesn't know what he can do, why let him get the first shot?). If Sophia shows up, Sayuri could worry that she could be collateral damage if a fight started. Her presence would also make it easier for Sayuri to take the "We'll settle this later" approach, and withdraw rather than attack him in front of an eyewitness who doesn't know the whole story.