To make it no is vinegar added, so there is no sour aftertaste. You add water to make a paste.
It is sold prepared in tubes or powdered.
It is usually served with oden, and some dumplings, and to add zing to some sauces.
Literature & Lore
Japanese school girls teach other other that if you put karashi into your purse, you’ll get a boyfriend (“kareshi” in Japanese.)