Yoshin-ryu is a specific style of Jujutsu (the art of flexibility)
His name means:

That's to say, a school transmitted to develop the spirit.
With the above meanings in mind, one can say that the ultimate purpose of studying Japanese Budo (martial ways) is to cultivate the mind through the practice of matrial arts, and to spread this method of cultivating the mind as well as the techniques of ju-jutsu into the world.