Mmm... there isn't too much extra to comment on with the Katsumi's and Michiru's paths.  They are of about the same length as the previous two (which means about one and a half times as long as the average charage route) with a lot of buildup before the relationships actually form.  That was my complaint with the other two, and that hasn't changed here.  Similarly to the other routes, I felt that the drama actually inside the route was a bit lacking compared to the common route.  Katsumi's route