Oliver,

most "difficult" and/or popular restaurants open reservations 2 months in advance (ex. Narisawa,Den,Ryugin,...).
There are exceptions though.
Some want your hotel to call them, others don't.

Apart from that, I want to propose to read www.tabelog.com and leave aside the Michelin guide for a while.
Since money is not an object, open tabelog, sort by score (>50 reviews) and go to all of them