Huh, didnt realise they had one to use. Every time we have tried to pay with card in japan it has been either impossible or a huge song and dance, even involving the old click clack slide impression carbon paper tools.
Smaller towns are a bit of a different story though.
The Tokyo Metro booth at Haneda doesn't accept credit cards though, I had to withdraw cash in order to get a Pasmo (the JR booth was already closed for the evening).
At restaurants, cafés and small stores it was usually either cash only, or cash plus a combination among the dozen mobile payments solutions that exist in Japan. Very confusing.