Chen Yuan-ping and the three ronin . Chen Yuan-ping (c 1650) was a Chinaman who fled to Japan after the fall of the Ming dynasty. In the Kokushoji temple in Edo he taught three ronin (masterless samurai) the secrets of kung-fu (kempo in Japanese). Each of these ronin went their separate ways, improved what they had learned and founded the first jujitsu ryu from which all the others sprang.

There are two main problems with this story, the martial art and the date. Kempo is very different from jujitsu so it is not a likely "seed". It could not possibly evolve into all the myriad forms of jujitsu in so short a time. Which brings us to the date which is far too recent. Documentary evidence pushes the roots of jujitsu far further back.
Why then is this story so widespread? One of the reasons is probably the date. That time was enormously turbulent for China. It marked the overthrow of the Ming dynasty by the Manchu dynasty and the destruction of the Shaolin temple. The Shaolin temple dominates the histories of the Chinese martial arts. According to legend, only five monks survived its destruction and each of these founded a kung-fu style from which all others came. The story of Chen Yuan-ping can be read as an attempt to attach jujitsu to this legend.
None of this means that the story can be entirely dismissed though. The political turbulence in China and the destruction of the Shaolin temple (or temples) were historical events. As a result, monks and warriors exiles would have turned up in Japan. It is easy to imagine someone like then joining a band of ronin and later on forming a ryu.

Akiyamma and the willow tree
Akiyamma was a physician from Nagasaki. He travelled to China in search of new knowledge where he learned 28 ways of resuscitating apparently dead people. He also encountered a martial art called hakuda which combined striking with grappling.
When he returned home, he began to teach what he had learned but was unable to attract enough students. Disheartened, he travelled to the Tenjin shrine for a hundred days to meditate and worship. It was here that he got lost in the forest in a violent snowstorm and had his revelation. He saw a pine tree that had been shattered by the weight of the snow next to a willow which was unharmed. The willow had "defeated" the snow by yielding to its force and springing back.
Akiyama applied this concept to his knowledge and developed it into 303 separate techniques. He founded the Yoshin-ryu (willow tree school).

China again. In ancient Japan, claiming a Chinese origin lent something an air of learning and respectability. But there is much more then than in this story.
Firstly, there is the implied understanding that atemi and kuatsu are two sides of the same coin. Many atemi strikes are into the meridians studied by traditional Chinese and Japanese medicine.
The best part of this story though is the perfect illustration of the central principal of ju. Too often, this word is translated as things like "gentle" or "flexible". These words may be linguistically accurate but they create the wrong impression. Jujitsu is not "gentle" in the sense that it does not apply force to and enemy. Neither is it "flexible" in that it always moving around an enemy. Jujitsu is "un-resisting" in the sense that the attackers movements are used to form a defence.
An excellent example of this is the kick defence osoto-garuma because it looks like the very opposite of ju. In its crudest possible form, the attacker kicks straight forwards and the defender steps diagonally forwards to the outside of the kick and bashes against attackers upper body. The attackers body spins backwards in the air and then slams into the ground. At first sight, this looks like pure brutality and for a very good reason - it is. The attackers force is met head on with another force and the drop to the ground is spectacular and certainly not gentle. But look again. Why does it work? It works because the force backwards the attackers upper body complements the forwards force which already exists in the legs. This produces the rotation around the centre of gravity that is the main part of the throw.
So, where another martial artist might have seen a kick as a force to be dealt with, a jujitsuka sees an incomplete osoto-garuma. The principal of ju demands that that the kick itself is unresisted so that the technique itself is completed. The fact that this completion involves moving towards the attack with a strike in no way invalidates the central principal.