In the Kuroomasu puzzle, you need to place black marks in the boxes so that the following rules are observed:
To facilitate the solution, you can use marks with crosses, they do not affect the solution. With the help of the highlight, it is easy to understand what exactly is not being respected in the solution process. When all the numbers turn green and there are no red areas or black cells outlined in a red border on the board, this means the puzzle is completely solved.