Jujustu is a Japanese martial arts style that focuses mainly on taking down armed or armored opponents with no weapons or a very short weapon. Its main focus is based off grappling. Jujustu was developed in feudal Japan to fight against the samurai at the time. Since it focused on combating an opponent who was armed or armored, the style was able to handle and defeat the samurai of the feudal age. Practitioners of the style found that striking an armored opponent would prove ineffective, so to make Jujustu a dangerous form of fighting to counter the samurai, they focused mainly on grapples such as pins, joint locks, and throws. These grapple techniques were developed on the principle of using your attacker's own energy against him instead of using your own energy against him. Unlike most martial arts such as Karate or Muay Thai which focuses on striking, Japanese Jujustu focuses and emphasizes on a system of throwing, pinning, and joint locking. Striking techniques are considered less important in this style when you are fighting an armored opponent.

There are many different derivatives, or variations, of Jujustu today. Jujustu has become the foundation for a variety of martial arts styles over the years. Instructors of these variations simply added new techniques and tactics into what they were originally taught.
Akido is a defensive style that focuses on preventing harm to either attacker or defender. Akido comes from the derivative of Aiki-Jujustu.

Bartitsu is a European variation that combines both boxing, savate, and a form of sick fighting. Bartitsu was developed by Edward William Barton-Wright and he developed it as a self-defense style.

Judo is a famous variation of Jujustu, and is now a classic example of a sport that is derived from Jujustu. Judo involves breaking an opponents balance as you grapple them and use their own momentum against them. What makes Judo different from Jujustu is the fact that Judo emphasizes more on Kuzushi, the art of breaking balance, than Jujustu does. With Kuzushi, Judo can lead to striking an opponent along his weak lines.

Brazilian Jiu-Jitsu emphasizes ground grapples more because it was thought to be efficient and mush more practical than basic Jujustu. It was brought to Brazil in 1914 by Mitsuyo Maeda.

Samba is a Russian variation and has a higher occurrence of leglocks. Its developer, Vasili Oschepkov, was one of the first foreigners to learn Judo in Japan and earned a second-degree black belt.

Jujustuhas been around for a very long time and has had many more variations and derivatives to it.