Thank you very much for such quick chapters
I don't understand the order of events. Why did sakurai turn up behind the school? I assume because one of the gang of delinquents left her a note asking her to meet there, but then why did the gang of delinquents seem surprised when Sakurai turned up and decide to change their plans? And how did sensei know that Sakurai was going to be trapped and assaulted by the delinquents? he was invited behind the school but how would he know that the gang would also invite Sakurai? A hunch?
Also, I don't understand why sensei would prefer to use the boy that he went to all that effort to separate from Sakurai? Now that boy and Sakurai are going to much closer after Sakurai has been saved by him? Surely he'd prefer to make an excuse to the other teacher and stop the delinnquents himself. Sure he might be worried about the pen, but still, isn't he more worried about Sakurai getting banged by delinquents or falling for another student?
Also, banging that teacher is going to cause that teacher to bother him more and give him less time to stalk Sakurai. It would have been better to just get the teacher drunk and chatty and find out whether she checked what was on the phone or if she made any copies, then get rid of any data and create distance from her. Having sex with her is just going to make that teacher more of a nuisance.