We like Mitake

Björn Buckwalter
Many nice problems on boulders spread along the river bed, including the classic benchmark problem Ninja Gaeshi. Easy access from Tokyo by train and on-site pad rental at the Manunga 2nd hand outdoor store (opposite the 7Eleven) make this a perfect destination for business trip weekends.
Eddie Gianelloni
Mitake is situated on a nice river adding a very nice ambiance to the boulders scattered around it. There are super classic problems of many grades. The Ninja boulder is the most popular area with problems v5 and up. A bit crowded on weekends and holidays, due to it's proximity to Tokyo.

Eirik Fernandez Cuesta
Small but beautiful area near Tokyo. Gets crowded with friendly climbers all the time.