PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s)

Theme: Multiples of 3

Author/Opus: This is the 62nd puzzle from our contributing puzzlemaster JinHoo Ahn.

Rules: Shade some empty cells black so that each number indicates the total count of white cells connected vertically and horizontally to that number including the numbered cell itself. Black cells cannot share an edge, and all white cells must belong to a single connected group.

Also see this example:

Difficulty: 1 star

Time Standards (highlight to view): Grandmaster = 1:00, Master = 1:15, Expert = 2:30

Solution: PDF and solving video.

Note: Follow this link for more Kuromasu puzzles. More Kuromasu can be found in Grandmaster Puzzles Quarterly Vol. 3.