Robbie Swinnerton makes a good point in his 2013 summary about restaurants serving game in Tokyo. In my limited experience, deco does a good job, especially if you catch them on a good day when they serve badger a la royale, or perhaps whole woodcock in red wine sauce, but during season they almost always have japanese colvert, at least, which Boucherie du Buppa is also famous for. Abasque is maybe a bit rougher around the edges, but it's hard to fault their wild boar in red wine sauce. There's always a bear and more at La Chasse, and speaking of bear, nabe season is the season to try matagi.
I tried to book here http://tabelog.com/tokyo/A1311/A13110... a while ago but couldn't, and didn't try again.