Because it is a simple condiment, you can make your own yuzu kosho pepper. Prepare the same amounts of unripe green yuzu rind and green chiles (after the stem and seeds are removed), along with salt that accounts for 20% of the combined amount of the yuzu and chiles.
Wash the yuzu and chiles thoroughly and wipe off any moisture. Remove the stem of the yuzu, peel the skin, and mince it.
The white pith part gives off a bitter taste, so remove it as much as possible. Make sure you wear gloves before treating the chiles.
Cut them in half lengthwise and remove the stem and seeds. Put the chiles in a food processor and mince them.