Masunaga was the founder of the Zen Shiatsu which was his main contribution to shiatsu.

"Zen" is a form of the Buddhist belief. Shiatsu is a technique of moving muscles and nerves around with hands and fingers to keep them healthy and relaxed.

That is a good question that I am not able to fully answer myself. There are several that I know of:

Zen Shiatsu - developed and popularised by Shizuti Masunaga (possibly the most popular form)

Ohashiatsu - Pioneered by Ohashi

Watsu - a water based shiastu

Movement Shiatsu

Shin So Shiatsu

And there are obviously more

I have studied Zen Shiatsu and don't know very much about the other forms, but I do believe that Zen is the main form that influenced the others...

Tempaku contribution to shiatsu was that he thoroughly researched the origins of shiatsu therapy and reported it.

Shiatsu is a Japanese form of acupressure.