I have always been fascinated by archery, and began practicing at the age of 14. I would cycle every Sunday about 10 miles to a field archery site atop a wooded hill, shot for about an hour and then cycle back (sounds idyllic but that hill was steep!).
Naturally when I started to learn Ninjutsu about 10 years later the Japanese art of Kyudo with the unique asymmetrical bow or yumi was a draw. Looking through Hatsumi sensei book 'History and Tradition' there are a few pictures of the hankyu or half bow that was used by ninja. The pictures showed shooting from cover, lying on the back and bracing the bow with the feet, and a drawing of a ninja riding a boar while shooting a bow!
With these images it was not straight forward to get a sense of the ninja style of shooting; however there was some very useful information. The bow and arrows were carried concealed in a bamboo tube, this meant it was unlikely to be a thick powerful bow as it was half the length and slender enough to fit inside the tube with a few arrows. Therefore the reduced draw weight and size of the bow necessitated its use at relatively close quarters and from cover - an ambush weapon.
It was also used (as in a lot of medieval archery) to not only shoot people, but to start fires with flame arrows; to send messages bound to the arrow; or as a signal either visually or audibly by cutting holes in the arrow head to make it whistle or screech in flight. Comparable examples of this are found in many western archery practices of the time period.
There is speculation that a messenger line could be shot across a space and provide an escape route, however the low draw weight and short range make this doubtful in itself. The most likely scenario would be to shoot a thin light weight line to an awaiting accomplice, who would then use the light weight line to draw across a heavier sturdy rope to be used for escape or infiltration.
Shooting methods would have to incorporate a way of firing when behind cover, when standing and when in elevated positions (trees, walls, rooftops) and it would be expected that these kamae or stances would be comparable to the unarmed kamae that the ninja learned to fight with. These positions are below, and are not too dissimilar to some kyudo stances.
The last two are kamae that can be used for close quarters defence when the arrows run out and your opponent runs in. The techniques somewhat similar to Jo and Hanbo techniques due to the length of the bow.
The mechanics of shooting would be the eastern thumb draw (the author has always used a western draw so these pictures reflect this). The arrows would be either in the hand or in a fabric quiver so as to not hinder rolling once the arrows were removed. One of the fastest ways to shoot would be to have the arrows in hand, but they would not be many in number as a large amount would be noisy and time consuming to organise and shoot. It is surmised that a number between three and nine would be used, purely from ease of carry and the Japanese love of numerology.
This is the authors own view of archery in Ninjutsu, and is based on his experience in archery and Ninjutsu.