Uber is still Uber in Japan, although they've partnered with limo car companies to provide the service. I'd say there are about 100 - 200 Uber Black drivers in Tokyo and the service is more costly than regular taxis. I use Uber Black for trips to Haneda, as they are basically the same price as a taxi and also for local trips when there are more than 4 passengers. Usually, if we have a business meeting or event and there are 5 or 6 people, it's more cost effective to hire an Uber Black Van compared to two taxis.

Grab is planning to enter the Japan market this year by partnering with one of the large taxi companies.