I just looked at the plot canon guide website by Tiamat I think. It’s a very excellent work, very satisfying, in-depth, and very good, if I may say so.
I am especially interested to share some perspective on the Satsui no Hadou and the Shun Goku Satsu.
Satsui no Hadou = Murderous Intent. This Intent, as so named by Capcom, is not exclusive to practitioners of lethal martial arts. In fact, it is latent within all human beings, however, it is intensified by contact with death, rage, and desire for vengeance. This is what it means when it is said to the warrior “Your greatest enemy is yourself.”
In fact, the warrior believes that when he steps onto the battle field, his sole and entire aim is to eliminate his opponent, “kill all who stands in your way, be it God or Buddha…”, puts it very well in Kill Bill 
However, he must guard himself from developing the intent to kill, that is, he fights solely to kill. There is a very thin limit between what the warrior believes in battlefield, and what it might be perverted into, therefore, Satsui no Hadou.
A warrior possessed by Satsui no Hadou is also prone to demonic possession, they are not necessarily exclusive to each other. One can cause another, or that one can lead to another. Satsui no Hadou is nothing mystical, it’s not fantasy, it’s very real, and it starts by feeding and nurturing anger and lust in your heart. Have you ever felt invincible and fearless when so provoked to blind rage? I know I have, the rage is nurtured to such point that it consumes the person and gives birth to the Murderous Intent.
You don’t have to be very strong to possess Satsui no Hadou. In fact, a warrior is supposed to be more resistant (more able to control) such rage by training his body, soul, and spirit in harmony.
Therefore, it is sometimes said that an unskilled man (in the arts of killing) can be more a warrior than a skilled man. The difference lies in the intent.
Shun Goku Satsu = Instant Hell Murder. What happens when it is executed is that, physically, the one who performs the deadly move hit, with great strength, speed, and accuracy, all the vital death points on the victim’s body. I personally know of six vertical death points, and one more (the heart) on human body, the rest I do not know, but I hear that there are more such spots.
Spiritually, it is as the website so well say, it literally sends the soul of the victim to hell. Soul = the personality, the real person that encompasses the mind, preferences, thoughts, feelings, etc. Hell is usually understood as a place of torture for evil angels (and gods), therefore, demons. It might surprise you to know that Hell is never intended (created) for human beings, but for devils only. Scripturally speaking, the only human being that would be sent to Hell are the Antichrist and the False Prophet. It is never meant for human beings.
This move is very deadly, it strikes both body and soul of the victim.
Is this technique real? Does it really exist? I can’t say, I have seen really amazing feats performed by martial artists, I can surely say that a technique which strikes at death points on human body with great accuracy, strength, and speed is very possible. Although I can’t say how many death points can be targeted at a time.
Because Saiki’s already said that it was published by Shogakukan in 1998 under the Wonder Life Special label. No one seems to know what the title is, so it’s difficult to pinpoint it. If you still think Dash no Chris will know more about it, I’ll try emailing him.