“殺気-Sakki and 察気-Sakki”
Here is an excerpt from the book “Bufû Ikkan” by Ben Jones-Shihan I found to be very helpful.
“Many people know of the Sakki test (see Chapter 13). Many people also carefully explain how sakki means killing intention, and the purpose of the test is to sense it and protect oneself. So far so good ‑ but unfortunately Dr Hatsumi does not often write it as 殺気 (sakki) but 察気 (sakki), i.e. not the ‘killing intention’ test but the ‘sensing intention’ test. You may not find this distinction important, but I believe it is a vital point. ‘Killing intention’ is something that is naturally emitted by animals (including humans) when they attack something. There is nothing special about it, nor any need to test it. However, ‘sensing intention’ is an ability, which many animals appear to possess, but many humans have lost. It may still remain to the degree that some people can sense when they are being watched ‑ and in everyday conversation the word ‘sixth sense’ is often used ‑ but is normally underdeveloped. For some reason, training in the Bujinkan helps it develop. But if it just stopped at the stage of being able to sense Dr. Hatsumi striking from behind, it would have absolutely no value. It has got to progress on from there to the level whereby you can sense the ‘intention’ (written with the character 気 (ki), familiar to many as the concept of ‘ki’ or ‘chi’ energy) of the universe. If you achieve this, you may be able to avoid a dead branch falling out of a tree (which has no ‘killing intention’), or sense the flow of events around yourself to avoid problems.”
You can purchase the online book here! http://www.japanesetranslations.co.uk/bujinkan/book.htm
Zentai Martial Arts Ft. Wayne Indiana