Koretoshi Maruyama was born in Nihonbashi, Tokyo, on October 5, 1936. He graduated from the Economics Department of Keio University in March of 1956. He became interested in the martial arts from his Middle School years, and at his father’s urging he took up Judo and earned a black belt.
In the spring of his third year of college, he began to develop doubts about the martial arts of judo, wrestling and boxing, which emphasized a mere contest of strength. At this point he entered the Aikikai, as well as the Keio University Aikido Club. It was here that he found in Aikido what he had been searching for all those years, a martial art which did not depend on strength, and taught the right attitude of mind.
After he graduated from Keio University, he continued his training in Aikido, while working in the family business.
In 1967 Maruyama sensei become a full time professional Aikido instructor, under the tutelage of the founder of Aikido, Morihei Ueshiba, and dedicate himself to the martial art that taught the principles of mind and Ki.