An
Aikido school / organisation founded by one of
O'Sensei's pre-war students
Gozo Shioda.
It emphasises building a strong individual and team spirit through gruelling training and strict discipline. Some Aikidoka find the methods employed by the Yoshinkan to be a bit militaristic.
The founder himself (Kancho) never spoke of ki in his writings, apparently finding the term a bit loaded and preferred to refer to the concept as Kokyu or breath power. His book "Total Aikido: The master course" illustrates some of the kokyu party tricks he would demonstrate to students to show them what could be done with solid training and an understanding of body mechanics.
On the technical side Yoshinkan de-emphasises the weapons work so integral to Aikikai / Iwama style Aikido and prefers to work on kamae (stance)