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 is your classic 'blood-related imouto route', with some of the same difficulties other such heroine routes share (inevitably) and it follows the usual pattern of 'blind love>realization of others' reactions>worry and fear>resolution'.  The main difference is that the fantasy elements involved in the story in general allowed for a different resolution than is the norm and that there was never any opposition or hesitation from the group of friends.  The ending is - like in the other routes - pleasing... though since she is the VN's resident loli, I think the lolicons might feel weird about it.

Michiru's route... is your classic 'osananajimi' route... there were some differences, but the big issue - as always - was the protagonist getting around his tendency to see Michiru as 'one of the guys', though it was perhaps less problematic than is the norm in most osananajimi routes because of the way the common route sets things up. 

Overall, this VN is a high-quality charage, with the drama focused in the common route for the most part.  There are some parts that grate on the nerves, but that is inevitable due to my tastes, so people who like this type of VN will lap it up, lol.