These balls, made by Cosmo Power, cost a few hundred thousand yen and can be used as a Tsunami shelter. It seats four (small) adults and can double as a teeny, tiny playhouse for kids until needed.
Sadly, they’ve been working on these things for years yet shipped only two so far. This is especially tragic in light of current events but it’s an ingenious way to survive a deluge. I wonder how long it will last on a playground until it starts to break, thereby reducing its utility.