This brings us full circle to the scene we saw in 15.1, which was when we first saw the "N doesn't exist" moment in the restaurant, though that time we were seeing it from Hiruma's perspective, but this time we're seeing it from the booth behind him, where Shindou is sitting.
Speaking of Shindou, his prophetic dreams of people dying are one of the last major overtly-supernatural elements of the series left, and chapter 14.1 and 14.2 have some surreal imagery of him at a computer interspersed with panels showing an overflowing bath tub like the one Sanae drowned in, along with what appears to be an older Shindou sitting in prison. I'm guessing we'll be circling back to that scene in the next chapter.
Or, to put it another way: fucking run, Hiruma. That boy's sus.