HISTORICALLY Yoshin Ryu Jujitsu, the "School of the Willow Heart" or "School of the Willow Spirit," presumably founded by Akiyama Shirobei Yoshitoki, a physician from Nagasaki, is one of the Edo-period jujitsu schools that is best known here in the West. This style or ryu dates back to sometime before 1671. Yoshitoki felt that the jujitsu techniques he had learned were not sufficient in number, so he retreated to Tenmangu Shrine, where he devoted himself to meditation for one hundred days, during which time he developed 303 techniques of his own. One snowy day when Akiyama Yoshitoki was still on retreat in Tenmangu Shrine, he happened to notice a willow tree on the shrine grounds. Despite the recent heavy snows, this willow, unlike some of the other trees on the grounds, did not have even a single branch broken. The Willow branches simply yielded and allowed the snow to fall off, thereby saving the tree. This yielding principle was not only understood to be an essential element of the warrior arts of ancient Japan, but have been perfected through the test of time...
Classical Fighting Arts of Japan,
A Complete Guide to Koryu Jujutsu
Serge Mol, 2001
your buddy was right, this is an old classical style, jigoro kano studied it as well as many other styles before creating judo, as did professor henry s okazaki before creating danzan ryu jujutsu.
many arts, like shindo yoshin ryu jujitsu (what hironori otsuka studied before making wado ryu karate do) to takamura ha (family) shindo yoshin ryu jujutsu...all stem from the original yoshin ryu. as far as i know, it is not THE oldest, but fairly close..it is very old. how authentic it is today is anyone's guess.