Uber isn't shy about its plans: it wants to expand its taxi partnerships "nationwide," a spokeswoman said. You can already use its app to connect to car services in Tokyo, but this would represent a significant expansion of its ambitions.

There's a competitive reason for Uber to work with its erstwhile enemies in the taxi industry: ridesharing giant Didi Chuxing is hoping to offer ride hailing in Japan with SoftBank's help. If Uber doesn't make inroads now, it risks having to exit the market like it did in Didi's native China. There's also the matter of mending Uber's corporate image. Recently installed Uber chief Dara Khosrowshahi has spent much of his time undoing the antagonistic approach of his predecessor, and cooperation with taxi companies (however limited) might play a role in changing people's minds.