Okinawan “yushi tofu” made from

Here in Okinawa where I'm currently travelling, there is a dish called "yushi tofu" (Japanese: ゆし豆腐).

So far I've only noticed it offered as a variety of Okinawa soba. (Okinawa soba is different to regular soba made of buckwheat.) I tried "yushi tofu soba" tonight in Naha and enjoyed it – but I'm still not sure what it actually is or what it's made from.

^{Image thanks to the Japanese Wikipedia.}

I've asked a few locals and none have been able to tell me what it is. English Wikipedia doesn't cover it and the mentions it gets in the Japanese Wikipedia do not translate well with Google Translate.

I'm pretty confident that "yushi" is Japanese "油脂", which means "fats and oils" – but that doesn't tell us very much.

In particular, apparently the word "tofu" is sometimes used for foods not made from soybeans so I would like to know if this is made from soybeans combined with fats and oils, made with the fats and oils that can be extracted from soybeans, or is made with fats and oils rather than soybeans. Or something else (-: