Within 300 km radius of Tokyo - Coastal/seaside destinations in Japan for nature and relaxation? [duplicate]

Since I'm planning to visit Japan for 10 days and plan to apportion 5 days to Tokyo, I thought to reframe this question inside a 300 km radius around Tokyo. 300 is just an estimate; I'm not strict about this. Moreover, I'm curious to know if where urban Tokyoites go, for want of a seaside/costal region for picturesque, scenic relaxation, resembling that of a nature getaway/resort/retreat. I tried https://www.jnto.go.jp/eng/location/interests/index_th_10.html and

such as it's written in the last paragraph here, I equally want: 'We love rocky beaches, nature hikes, history, the smell of ocean air, the scenery of water, and ... to experience Japan in a smaller town way'

but I would like the satisfaction of these criteria:

1. I want to avoid bears and lethal animals.
2. Due to possible radiation, I'd like to shun Fukushima and its surroundings.
3. I won't drive, so must rely on public transport and walking (over reasonable distances).
4. I want to evade temples and all buildings related to religion.