This is literally some of the most expensive real estate in the city, and office space in central Tokyo is not cheap. I'm amazed that they can find enough tenants to sublet this at a profit.
That said, WeWork does have a Japan-only advantage here, because startups generally find extremely hard to lease office space there: even if they can find a landlord willing to take a punt, they are often required to pay one to two years' rental as deposit. [1] This won't help them scale outside Japan though.
[1] https://www.venturejapan.com/doing-business-in-japan/how-to-...