Good question. I suppose he gave her a convenient excuse before departing, like some small group trip to the West to study or something or other. Maybe later his mother can see what he has to deal with for the benefit of everyone else. Kurama might be sad that he has to show her that he isn't the son she thought she had, but maybe Botan can speak about the good things he's done to keep her happy and safe. That would go equally for everyone else in the city. Kurama's pretty modest unless he's pissed, and hopefully mama Minamino won't have to see his rage.

I'm trying. 

Okay, first try. Wanted to get into the analytical side of him on this and have him so deep in thought that it's beginning to hurt the guy. Botan's arrival was timely--almost too timely--so if he's busy thinking about these random suicides, and Botan shows up out of the blue without being prompted at all, he's going to put it together that there might be something to all of this. Hope it was okay.