[godwine]

Ok, others can correct me if they want, since my "true" local expereiince are from almost 20 years ago, and the last few years I have only been taking 2 weeks trip to Japan.

But for beaches, you can try the following:

Simoda
Ito
Hiratsuka
Chigasaki
Kamogawa
Hitachi
Takahagi
Ishomaki

What kind of things do you plan on seeing? I am not totally sure if you really need a full week in Osaka/Kyoto, so do drop by the surrounding cities.

Tokyo is big, but not big enough to last you 2 weeks, Nikko is more like a day trip, 2 at most. Mount Fuji is accessible from Hakone (from Odawara) and Atami, both are onsen resort town, so I take that you will be spending a few relaxing days there, but still, 2 weeks in Tokyo is a bit over kill.

For a 6 weeks Intinerary, I will consider fitting in Kyushu and Shikoku, but its your choice.