Sou-Setsu-Ken (Chinese: 双截拳 Shuāng Jié Quán, lit. "Twin Sever Fist"), alternatively known as Sōsaiken, is a fictional martial arts style practiced by Billy and Jimmy Lee. It is loosely based on the real life martial arts style of Jeet Kune Do.
The Sou-Setsu-Ken is a fictional legendary Chinese martial art and a steady concept in the Double Dragon series (in some media, it is stated that the Lee brothers co-founded the system themselves). It is a secret fighting technique that, as a result of a rigorous training of mind and body, allows its practitioners to channel their inner energy to perform both offensive and defensive maneuvers that would otherwise seem impossible for a normal human being.
Depending on a particular game's documentation and due to different interpretations during localization, it has been known in export releases under different variants of the same name, such as: Sōsaiken (Double Dragon for NES and Game Boy), So-Setsu-Ken (Super Double Dragon), Sousetsuken (Double Dragon (Neo Geo)), Sosetsu Ken/Sosetsu Arts (Double Dragon (mobile)), Sōsetsuken (Double Dragon IV), just to name a few.
Ironically, the fact that the Lee brothers had mastered this technique was actually the reason that brought their feud with the Black Warriors in the first place, as Willy Mackey, their leader, coming into knowledge of its existence, ambitioned to have it for himself, so he planned the kidnapping of Marian, Billy Lee's girlfriend, in order to lure him to his hideout and force him to surrender the scrolls (or tomes, depending on the game) that contained the secrets of the Sosetsu Arts.
It is also eventually revealed, although not to much surprise, that the scrolls containing the secrets of the Sosetsu Arts do not yield any magical fighting abilities, nor do they teach how to procure oneself with such; all they do is teach advanced fighting techniques, but the secret of its power lies in the inner strength of mind and body of the individual himself.
The Sou-Setsu-Ken is loosely based on the real life martial arts style of Jeet Kune Do (截拳道), also known as the "Way of the Intercepting Fist". In supplemental materials for the original Double Dragon, Sou-Setsu-Ken is described as a "complete collective of various martial art styles", combining techniques from other styles such as karate, tai chi and Shorinji Kempo into one (with other styles mentioned in later versions of the description). Its representative technique was originally said to be the "Whirlwind Kick" (旋風脚 Senpū Kyaku ), which is the last technique the player acquires in the NES/Famicom version of the first game, although other techniques are mentioned in the Double Dragon Advance version of the description.
Return of Double Dragon establishes that Sou-Setsu-Ken is divided into two schools: the Southern School (南派双截拳 Minamiha Sou-Setsu-Ken ) practiced by Billy Lee, which focuses on agility and flexibility; and the Northern School (北派双截拳 Kitaha Sou-Setsu-Ken ) practiced by his brother Jimmy Lee, which focuses on strength.
The Gen-Satsu-Ken (Chinese: 幻殺拳 Huàn Shā Quán, lit. "Phantom Murder Fist"), a deadly secret martial art known to be used only by the highest commands of the Black Warriors crime syndicate, opposes the teachings of the Sou-Setsu-Ken and both schools are known to have been in conflict for generations. Besides being a deadly martial art that rivals that of Sou-Setsu-Ken at an almost equal level, the technique is also known to employ black arts in its teachings, such as the creation of illusions, use of energy projections, and even the creation of magical beings that are blindly loyal to their masters.
- Jeet Kune Do, the hybrid philosophy of martial arts which Sou-Setsu-Ken is inspired from, was heavily influenced by the personal philosophy and experiences of martial artist and action films actor Bruce Lee, the founder of the system.
- A similarly named new martial art called "Sosetsitsu" replaced the Sou-Setsu-Ken as the Lee brothers' trademark fighting technique in Double Dragon Neon. However, keeping in tone with the game's '80s era culture homage, it is fueled by music mix tapes rather than in mind and body training.
- Even if both martial arts are different in name, form and lore, the Sou-Setsu-Ken's signature move, the "Hurricane Kick", can also be found as one of Sosetsitsu's main techniques, known there simply as "Spin Kick".
- The rivalry between Sou-Setsu-Ken and Gen-Satsu-Ken may be inspired by Hokuto no Ken's (known outside of Japan as Fist of the North Star) fighting styles Hokuto Shinken and Nanto Sei Ken.
- The Tatsumaki techniques from the Street Fighter series were probably based on the Sou-Setsu-Ken's whirlwind kick, although this is mere speculation.
- The Japanese language manual for the Sega Mark III version uses this pronunciation, as does the English manual for the NES and Game Boy versions.
- Double Dragon Advance ending.
- In Japanese, Jeet Kune Do is known as Sekkendō.
- Mark III/Master System Double Dragon manual
- Double Dragon Advance character profiles (Internet Archive, Japanese)
- Double Dragon Dojo - Source for the animations.