Yajisan-Kazusan is a puzzle type originally created by Nikoli.
Shade black squares in the grid so that all unshaded clues point to the number of black squares in the direction of the arrow. Shaded squares may not share an edge, and all unshaded squares must be connected as one group.
Clues may be shaded in. If they are shaded, they play no further role in the puzzle, and may be true or false.
See this example puzzle and its only solution.