Decades after winning a prestigious ninja tournament and claiming a mystical dagger meant to unlock a treasure-laden cave, the elderly master Mori finds himself unable to continue his personal crusade to recover the weapon—stolen years ago by his bitter rival Koga and lost to time. Recognizing that the dagger's retrieval falls beyond his aging abilities, Mori turns to his three trained grandsons, Rocky, Colt, and Tum Tum, enlisting them to succeed where he could not. The brothers accept the challenge to track down the stolen artifact and restore it to their grandfather's rightful possession, understanding that the dagger represents not only a family heirloom but a legacy meant to pass through generations via the tournament's victors.