Goutetsu, a very strong and fast Grand Master of martial arts created an offensive based fighting style which incorporates elements of karate, judo and taekwondo called Ansatsuken (Assassin's / Murderous Fist/ Satsui No Hadou) that enables you to channel chi power as physical energy thru your hands, because this art was offensive based it was created specifically to kill your opponent. The art was very very difficult to learn but also very very deadly and lethal at the same time, you could murder your opponent in a mere strike. The techniques of this deadly art included the dragon punch, hurricane kick and fireball, when students became of age & skill the advanced techniques were then taught which were the messatsu-gou-shoryu, messatsu-gou-hadou, tenma-gou-zanku and the deadliest technique of the art the shungokusatsu (instant hell murder/raging demon). Goutetsu trained many students in his time making them masters of Ansatsuken at his dojo, but he only trained 2 at a time of opposite character. This acheived two things- 1. It taught the student to learn from their counterpart's fighting style while developing their own unique individual style. 2. The interaction of both students training together made them stronger than they could have ever been if either had trained alone. Goutetsu was soon training students Gouken & his younger brother Akuma (Gouki in japan) for many years at his dojo and although Gouken learned much faster, it was Akuma who was stronger but they were still just about equal in skill.....(Goutetsu means "thunder iron".....Gouken means "strong fist"....Akuma means "strong demon", but in terms of strength not possession). After his training was completed Gouken began competing on the circuit and became a very respected and dangerous streetfighter winning many martial arts championship titles without even having to use the killing techniques in his fights, after awhile Gouken became very anxious to begin teaching so he retired & opened a dojo of his own. Gouken disliked the killing aspects of ansatsuken so much that he removed them and created and refined his own new version of the Ansatsuken art including a completely different form of chi gathering than what he was taught by his master and the art became a true fighting style made especially for combat and self defense. Gouken first taught Dan for some time, long before Ryu and Ken but was kicked out of his dojo because his heart was too filled with hatred and revenge for Sagat so he returned to Hong Kong and trained himself using his own "style." Years later, Gouken realized and decided that continuing the 2 student tradition Goutetsu used was much better than just training 1 student and started training Ryu and Ken. After his training was over Akuma found a cave on Gokuentou island in Japan, he embraced the killing aspect of the Ansatsuken art whole heartedly for what it was originally intended to be used for and wanted to be stronger and faster than anyone he ever challenged in battle so he stayed and trained there for years mastering every special move and technique he learned to perfection without flaw. Akuma visited Gouken back when Ryu and Ken were still "hatchlings". Akuma stated that he was the true heir to Ansatsuken, then Gouken stated that Akuma corrupted his "Hadou no Chikara". Akuma and Gouken began to fight as young Ryu and Ken watched, believing Gouken would win the match ended with Gouken's final blow, leaving Akuma sprawling on the ground and embarrassed. Gouki said we MUST and WILL come to blows again "in this lifetime'". After Akuma left, Gouken told Ryu and Ken, when my brother's power goes beyond my own the great disaster which is my brother you both will and must face with your own power... the power which I will pass on to you... "Wa ga ken no Subete o (All that is what my fist is), Hadou no Chikara o! (The power of the Hadou!)."
A few years pass, Akuma returned to his Master's dojo, Akuma challenged him and they fought. During their battle, Goutetsu wasn't moving like an old man as many would perceive just by looking at him but quite the opposite giving one heck of a good fight throwing, punching and kicking with lighting speed. Akuma marveled at his master's fighting spirit and being a very worthy opponent, after exchanging hits and blows for some time Goutetsu cupped his hand as massive flames begin to form in and around them as he prepared to throw a Messatsu Gou Hadou Super fireball at his pupil. Akuma seeing this, uses this as the perfect time to execute the Shungokusatsu........
.........Goutetsu died with a smile
on his face, most likely because it was the greatest battle of his life......after a second, Goutetsu's dead body sprays blood. Gouken witnesed the entire fight.
Akuma removed the beaded necklace(means the "strongest") that was on Goutetsu's neck and burned the "Kanji" symbol on because it symbolizes the strength and power of his fighting style. Wasting no time, Akuma began searching for his brother....
More years pass, Akuma finds his brother Gouken at his dojo in the japanese mountains. 
"Ah Brother, What Brings You Here"?? Akuma responded saying, "I told you brother we would meet and come to blows again, has it been that long that you've forgotten" 
and took a fighting stance. Gouken never wanted to fight his brother (even during their training years because of his tough acceptance of defeat from time to time) but he knew this day would eventually come sooner or later where he would have to fight him in a battle to the death so he reluctantly took his fighting stance. Both brothers stare at each other, they don't blink, move or make a sound...it was so quiet you could hear a pin drop, the leaves outside and chirps of the birds in the trees. Suddenly, Akuma immediately does his "Messatsu Super Fireball", Gouken steps to the side. Akuma punches Gouken, Gouken responds with punches of his own & does his "Messatsu Dragon Punch" striking 10 hits. Gouken throws air fireballs knocking Akuma down, he rushed in kneeing Akuma's stomach then imediately went into a hurricane kick connecting 6-hits and Akuma was thrown against the wall. Akuma gets up with blood dripping from the corner of his mouth, he throws a fireball and does 2 dragon punches 
. Akuma jumped in with an air hurricane kick but Gouken grabbed Akuma's leg and immediately went into his own hurricane kick and then did a 4-hit dragon punch, Gouken then did a "Messatsu Super Fireball" catching Akuma as he was falling down knocking him into the corner of the dojo . Back and forth the brothers deliver powerful blows to the other, each blocked with precision neither gaining the advantage. Akuma air hurricaned Gouken for 5 hits, Gouken connected his "Messatsu Super Dragon Punch" for 10 hits. Gouken then jumped at Akuma and threw two air fireballs into a 3 hit dragon punch but was weakening rapidly, Akuma jumped towards Gouken doing a dive kick and went straight into his "Messatsu Super Fireball" 
connecting for 9 hits. Akuma trips Gouken & drops both his knees into his brother's chest breaking his ribs. Gouken stood up exhausted & bleeding, Akuma said "Alas, You've Failed As Goutetsu Failed, I Thought You Wouldn't Hold Back Like Him...But Now Like Him...You'll Pay For Your Cowardice"....SHUNGOKUSATU"!! 
...bright white light filled the dojo intensifying like floodlights, it was so bright you couldn't even look at it. Every window and crack from the dojo was filled with protruding light, suddenly the light flashed red...an agonizing scream...the light then flashed back to white again and withdrew back into the dojo. Gouken's daughter who Ryu & Ken called "Little Miss" witnessed the entire fight, she wasn't heard from or seen again since that day. Ken was just returning from the United States and was anxious to tell his Master how he became the All American Martial Arts Tournament Champion, but upon reaching the dojo he saw the last of the white light withdrawing into the dojo. Ryu, who was competing in the SF1 tournament became the new champion was also anxious to tell Gouken how he defeated the Muay Thai Champion Sagat and how he scarred his chest with the dragon punch technique joined Ken later that day to find Gouken's dead body on the floor in the right corner of the dojo....but no one knew that Gouken didn't die, he remained in a coma for many years but finally awoke out it and began retraining to face his brother again in a true battle to the death bringing with him a new level of strength and wisdom and he reached a new level of mastery called "the power of nothingness" 
. Akuma was already gone but left 2 fading red spots and kanji symbol, he beleived with Gouken & Goutetsu's deaths was proof of his mastery of Ansatsuken making him the "Supreme Master Of The Fists". Akuma's fights by "the
harsh code of the absolute warrior". He had no qualms killing his teacher
and brother because he killed them in fair one-on-one combat. It didn't
matter who they were, the field of battle does not distinguish between
friend or foe. And he only fights and kills those who call themselves
warriors and trains in fighting, he travels the world for worthy opponents testing his skill and proving he's THE strongest warrior alive having NO equal........BUT after using the Satsui No Hadou for so many years, the negative energy of the martial art has fully taken over and consumed Akuma's entire being and having lost all humanity he's no longer human and is now controlled and taken the form of a full demon. He no longer has the warrior code he used to live by and will now kill anybody in a fight, unlike before where he only challenged opponents whom he deemed stronger than him and worthy to kill in battle.......Akuma is no more, he is now Oni.