of the Ueshiba family. However, aikido has developed into many styles, most of which were formed by Morihei Ueshiba's major students. The earliest independent styles to emerge were Yoseikan Aikido, begun by Minoru Mochizuki in 1931, Yoshinkan Aikido, founded by Gozo Shioda in 1955, and Shodokan Aikido, founded by Kenji Tomiki in 1967. The emergence of these styles pre-dated Ueshiba's death and did not cause any major upheavals when they were formalized. Shodokan Aikido, however, was controversial, since it introduced a unique rule-based competition that some felt was contrary to the spirit of aikido. After Ueshiba's death in 1969, two more major styles emerged. Significant controversy arose with the departure of the Aikikai Hombu Dojo's chief instructor Koichi Tohei, in 1974. Tohei left as a result of a disagreement with the son of the founder, Kisshomaru Ueshiba, who at that time headed the Aikikai Foundation. The disagreement was over the proper role of development in regular aikido training. After Tohei left, he formed his own style, called Shin Shin Toitsu Aikido, and the organization that governs it, the Ki Society (). A final major style evolved from Ueshiba's retirement in Iwama, Ibaraki and the teaching methodology of long term student Morihiro Saito. It is unofficially referred to as the "Iwama style", and at one point a number of its followers formed a loose network of schools they called Iwama Ryu. Although Iwama style practitioners remained part of the Aikikai until Saito's death in 2002, followers of Saito subsequently split into two groups. One remained with the Aikikai and the other formed the independent Shinshin Aikishuren Kai in 2004 around Saito's son Hitohiro Saito. Today, the major styles of aikido are each run by a separate governing organization, have their own in Japan, and are taught throughout the world. The study of is an important component of aikido. The term does not specifically refer to either physical or mental training, as it encompasses both. The kanji for was written in its older form as up until the Japanese governmental writing reforms after World War II, and now is more prevalently seen in its modern form of . This form has the removal of the eight directions denoting the pre and post natal energies of (Chinese – ) also known in the Art of Aikido as "Source energy". The character for is used in everyday Japanese terms, such as , or .