On an empty board, moving first is a decisive advantage: with perfect play, freestyle Gomoku is a proven black win. Renju keeps the 15×15 board but binds black with three forbidden patterns — double threes, double fours and overlines; black must win by skill inside the binds, while white hunts the binds themselves. The asymmetry is the whole design: black wins only by exact five; white wins by five, by overline, or by catching a foul — three doors against black's one. See the first bind for yourself: black has two open twos here, row and column, and one point would turn BOTH into open threes at once — that point is forbidden. Find it.
Finish this step to move on.