Before going to the black market merchant, I practiced joint attack techniques with Gwang-hyo, Won Seo-gang, and Geuk-hwan to strike Hu Il-hyeong. There was nothing particularly special about it. All we did was surround the enemy with a wide formation, coordinating our strikes and retreats in a pincer attack.
No matter how skilled the masters, joint attack techniques only mean something if their breathing and timing are in sync. If everyone acts arrogantly and rushes in disorderly, it only hinders things, so it's better to fight alone. Even when I roamed as a wandering swordsman, I fought like that.
The standard was to maximize the advantage of numbers: one person draws attention while others strike from blind spots. No matter where you go in the Central Plains, joint attack techniques are mostly like that.
I wondered if there could be more, but I've heard that the joint attack techniques of the Nine Great Sects, famous throughout the land, are on a completely different level. Wudang's Seven Star Sword Formation. Shaolin's One Hundred and Eight Arhat Formation...