The same rule covers fours: one move making two fours is a foul, even if both are mere rush fours — the rules count the fours through the stone, not the five-points. Here black's row and column each wait one stone short of a four, crossing at a single point; filling the crossing makes both fours at once, and under renju that is a loss, not a double threat. Note the contrast with white: white may play this exact move freely, and for white it wins on the spot. Find it.
Finish this step to move on.