I have a question about Nobuyuki and yandere in general. Is it a sign of insecurity because he has someone watch over MC so she won't run away? I would think he had enough confidence in himself to think that he'd be enough to make MC stay.
Rather than insecurity, I would think that it’s a lack of trust in his partner. Since she has proven that she’s not 100% about him, I don’t think he, as a yandere, would be comfortable with the possibility that she might get close with someone else/cheat/leave him. He can’t watch her all the time due to his position, so it’s only logical that he would assign someone else to do it in his place.
Btw I think in an event story? Or maybe one of the event story teasers? Nobuyuki insinuates that he would never let his partner get away from him. :O