These are starting to show availability for mid-November onwards. Prices look like ¥13,000-¥20,000, which puts them in a similar ballpark to Fairfields, the difference being Flex are in the center of cities.

These were all part of a Japanese business hotel chain until recently so they are small rooms (13sqm). No free breakfast for Platinum etc. and only 1 elite night credit per 2 night stay makes it unlikely I will stay at one. Better off with a Japanese business hotel.