A Fubuki Additional Puzzle is a grid of six by six squares or cells, that has been subdivided into six subgrids
The objective of sudoku is to enter a digit from 1 through 6 in each cell, in such a way that: Each horizontal row (shown in pink) contains each digit exactly once Each vertical column (shown in yellow) contains each digit exactly once Each subgrid or region (shown in green) contains each digit exactly once

Solving a Fubuki Additional Puzzle does not require knowledge of mathematics; simple logic suffices. (Instead of digits)

In each Fubuki Additional Puzzle, several digits have already been entered (the "givens"); these may not be changed.

The puzzler's job is to fill the remainder of the grid with digits –respecting, of course, the three constraints mentioned earlier.

A "good" puzzle has only one solution.