A brief history 

Known in ancient China as Moshou (hand rubbing), then Anmo (press and stroke), then Tui-Na (lift and grasp), oriental bodywork was introduced to Japan by Buddist priest around the 6th century and became Koho Anma. Therapy exclusively given by blind persons, Koho Anma was renamed Shiatsu Ho (finger pressure therapy) by Tamai Tempaku in the beginning of the 20th century. Tamai Tempaku is considered to be the real father of Shiatsu Therapy. Practicing and teaching Koho Anma, AmpukuHo (abdominal massage), Do-In (exercise and breathing), Tsubo Ho (acu-point therapy), western anatomy and physiology, he created a system that integrated these different modalities. This system was called Shiatsu Ryoho (finger pressure way of healing).

Development

Three of his main students developed their own approach of Shiatsu: 

Serizawa Sensei created Tsubo Therapy 
(Read - Tsubo: Vital Points for Oriental Therapy) 

Namikoshi Sensei and his son Toru developed Shiatsu as neuromuscular massage system without references to the oriental medical concept after World War II 
(Read – The Complete Book of Shiatsu Therapy) 

Masunaga Sensei (her son Shizuto) developed Zen Shiatsu, a system based on treating the meridian system of the body 
(Read – Zen Shiatsu, How to harmonize Yin and Yang for Better Health) 

Then many different variations of Shiatsu appeared and we can now count as many as 20 different styles of Shiatsu practiced worldwide.