Probably best not break out the champers quite yet. This is 'a deal in principle' right? No actual signatures?
We need to get their signature on a bit of paper to hold them to account while we raise internal legislation to 'dis-apply' the bits we don't like. I'm sure our Japanese 'friends' will see the reasonableness of this, particularly if we say we were under pressure due to a self imposed deadline.
They are reasonable people who are bound to accept our rationale.
Then we can break the party hats out....