I have no idea if the version that's going on sale via Emobile middle of the month has a different software image than the one sold in Play Store.
Went out to Akihabara today, from one end to the other. Not a single Nexus 5 case to be found.
On Docomo at least, no Google Wallet.
Trivial to get running on Docomo if you've already got an Xi contract with 3FF SIM:
1. Go to www.mydocomo.com, log in with your mobile number and password
a. sign up for moperaU service (6 months free, after 6 months you'll want to change it to moperaU light)
b. cancel your sp-mode service (save 315 yen/mo for those 6 months)
2. Put the SIM in the Nexus 5 and power it on
Detailed rundown for those with weak japanese-fu at http://www.aeug.org/drupal/node/22