Koji is a mold that is cultivated on rice and that is responsible for the sugarification of the starch in the rice as well as the production of other enzymes responsible for the taste of the sake.
Kojizuke is a pickling method for winter.
Best example: bettarazuke, using daikon. Has a sweet flavor and alcoholic aroma. The name derives from the "stickiness" (bettara) of this type of pickle.