I think it's perfectly understandable if you also look at how Japanese exchange bitFlyer has been seeing its trading volumes increase significantly. It might indicate that they are looking to use Bitcoin as a long term investment as people mostly buy hardware wallets for the purpose of using it as cold storage. I bought myself also a Trezor not that long ago. It comes at a cost, but it's all worth it since there is nothing more important than the security of my cold storage.
I think they bought hardware wallets, because the threat factor increase as Bitcoin's price and popularity increase. It is one thing to own Bitcoin,
but another thing to secure them. A hardware wallet gives you the best of both worlds... It has better security than your garden variety online
wallets and you can use it for cold storage.
.... The Japanese are going to kick the Chinese out of Bitcoin soon.