Benishoga is pickled red ginger root.  It is bright red and comes in long thin slices.  It should not be mistaken for Sushi ginger which is pickled in sweet vinegar.  Benishoga is pickled in plum vinegar, and it is sour.  Also there is spiciness from the ginger itself.

Benishoga is used for Okonomiyaki, Takoyaki, Gyudon, and many other dishes.  It goes particularly well with the sweetness of sauces and seasoning of dishes.