Heat the rice bran oil to about 180°C (350°F).
Combine the mayonnaise with the yuzu koshu paste.
Pat dry the soft-shell crabs and dust with the potato starch.
Fry the crabs in the hot oil until crispy, about 3 minutes. Drain and cut in half.
Halve the slider buns and toast the insides.
To build the sliders, add a spoon of mayo to each brioche base followed with a few spinach leaves, a crispy crab half, and close with a bun top. Serve hot.