Naisen means extend. This means that Naisen ryu is interested in extending oneself totally into every technique. Further this means that , unlike most japanese arts, one is expected to extend ones knowledge to other styles. Furthermore the emphasis is not on the founder, but rather on concepts.
Officially founded in the 1960's by a Japanese American named Kenneth Otaka. He had trained from childhood in Shorin ryu, but then after leaving japan he was exposed to Kempo and Wushu. He found that the traditional Japanese Shorin ryu was not fullfilling for him. After 25 years of training and achieving dan ranks in several styles (Yondan Shorin Ryu, 1st dan American Kempo and about 4 years of Wushu) he chose to found a new system. This system is based firmly in traditional japanese philosophy and technique, but has built in room for expansion and variation. For example each level of rank has a minimum set of criteria which individual instructors cannot change. However instructors are quite free to augment or add too these criteria. This allows for a common ground among practioners, but also variation from school to school.
This art differs strongly from other japanese arts on several issues:
The art is structured into 6 kyu ranks and 9 Dan ranks The student progresses from white belt to brown then to shodan (1st degree black belt). It takes the average student 4 to 6 years to achieve shodan. Ranks beyond this require a MINIMUM of as many years as the dan one is testing for. For example one must wait at least two years after getting 1st dan before one can even consider testing for 2nd dan.