They do buy from local steel wholesalers, usually up to a ton in bar stock every few years, at least that’s what it’s like in Sakai. That’s also why steels getting discontinued isn’t an issue immediately.
There’s also another thing going on. Hitachi is in trouble and they’ve been selling off a lot of their legacy subsidiaries.
Hitachi metal was sold and is now called Proterial. The owner is an American fund the Japanese often refer to as a vulture. Good old Bain Capital.
https://en.baincapital.co.jp/portfolio/proterial
The price increases are part of the takeover. There’s a chance they’ll sell it off once the books have been polished a bit in a few years. All of this doesn’t fix the issue of too little demand, though. In the long run takefu specialty steel will probably take over.