Within 300 km of Tokyo: Where for flora, landscape, nature? [closed]

You may not realize it, but that's actually quite a difficult set of conditions. One by one:

1. Well, this one's easy, there are no lethal animals anywhere near Tokyo.
2. Also not a problem, public transport anywhere around Tokyo is also easy. "Off the beaten track" means relying on buses instead of trains, but you certainly don't need to rent a car. But...
3. If you must be able to "see the ocean", only areas near the coastline qualify. However, more or less the entire eastern (Pacific Ocean) seaboard from Nagoya through Tokyo to Sendai is heavily industrialized, with only a few exceptions I'll get to later. (Check out a satellite map: not a whole lot of green on those coasts.)
4. Most of the few remaining bits are national parks, and in Japan, virtually without exception, any mountain or scenic little offshore island will have a temple, shrine or both plunked on top.
5. ...you do realize you're visiting Japan, yes, ? Maybe Mongolia might be a better idea.

So what does that leave us with? I'll throw out a few ideas. Note that all of these are popular with the Japanese as well, but tourism is pretty seasonal and it'll be fairly quiet on weekdays if you manage to avoid the major holidays.

• The Izu Peninsula, about 2-3 hrs south of Tokyo by train, is a popular hot spring area with bits of perhaps only 50% tamed wilderness, like the rock formations of the Jogasaki coast near Ito, and a bunch of good hiking trails.
• A bit closer to Tokyo, the southernmost bits of the Boso Peninsula are also a national park. Mount Nokogiri is the most famous spot around here, but (as usual...) it's encrusted with the usual temples and statues.
• My top pick for you, though, would be the Izu Islands, 108-354 km away from Tokyo and easily reached by ferry or short flight. All feature volcanoes, volcanic black sand beaches, hiking trails, hot springs, cycling, scuba diving and more. On the downside, there are (rare) habu vipers and a slightly elevated risk of being killed by a volcano, but hey, this is Japan we're talking about, you can get stomped to death by Godzilla (or, more likely, an earthquake) anywhere.