A much better map is here, on MapMyRide.
Here’s the map. There’s a run from Tokyo over Kogosaka Pass, then three loops: the Mt Fuji circuit (50.7 km), the Mikuni pass circuit (30.6 km, which goes back thru Kogosaka Pass), and the 17.7 km FSW circuit (which they do part before, part after,the Mikuni Pass circuit, visiting the Speedway twice). It ends @ the Fuji Speedway. Unlike the tradition in World Championship courses, there’s not a dominant circuit of 15 - 20 km which is repeated multiple times, so there’s a lot of options for Zwift.
Here’s the route profile:
There’s some serious climbs on this course. The Fuji Sanroku climb gains around 900 meters, putting it just below L’Alpe de Zwift in elevation, but not as steep (16.0 km, rather than 12 km). The Mikuni Pass climb is much steeper but with less altitude: around 690 meters in just 7.0 km, a 9.9% average. The reverse lap would be much more gradual.
It will be interesting to see what Zwift implements. The part thru urban Tokyo is probably way too complex. My guess would be the speedway will be tempting, a bit of work with the grandstands, but surely models exist already with all of the F1 games out there which can be licensed. While Mt Fuji is epic, that’s a lot of kilometers. So if I had to guess I’d guess they build the Mikuni pass circuit (30.6 km), with the Fuji Speedway circuit. They’ve certainly had long enough to work on it, and all of the loyal Japanese customers deserve something nice: Europe and the US have gotten all of the real-world routes so far.
Here’s satellite view of the speedway:
The red lines are from the RideWithGPS route which may not be precise (I’d think they’d be on the race track).
And here is an on-board video of a lap, and here is an existing game model.
So this would provide three obvious courses: the mountain circuit, the Fuji Speedway, and Olympic finale with the circuit starting and ending on the speedway, then the reverses. The climbs of Mikuni and Kagosaka passes would fill a bit of a gap between Epic KOM w/ Radio Tower and L’Alpe de Zwift in altitude gain, so a nice stepping stone there for people trying to make that leap.