Renju VCF #4996512 (7-move VCF)
To move: Black — find the move that forces a win by fours
Winning line
H6 → G7 → H10 → H7 → E7 → G9 → G10 → J10 → E10 → F10 → E8 → E6
Why this move works
The answer is H6. A seven-move VCF that drives White with forcing fours (H6→G7→H10→H7→E7→G9→G10→J10→E10→F10).
The decisive E8 makes two winning points at once; White cannot cover both, and E6 makes five. Never letting the chain of fours break is the whole trick.