Chapter 0 and Chapter 5 have been updated as well, since they're also part of Volume 2. The mangaka has hinted that she might go back and do a nipples version of Volume 1 if the nipples version of Vol 2 sells well enough, so if we're really lucky I'll get to go back and update the earlier chapters as well.
In the meantime there's still a few chapters left in Volume 2, so expect more soon.