Here is an interview with Hohan Soken who also references that Kusanku was frequently practiced with the "Jiffa" or hair pins in your hands.
FightingArts.com - Interview With Hohan Soken: The Last Of The Great Old Time Karate Warriors ? Part 1
Chotoku Kyan also taught many applications in Kusanku used the Jiffa. Here is a picture of the "weird chamber" I was referencing, but in the Yara Kusanku, which is one of the older versions of Kusanku the hand is completly behind the head. If you look at later versions the chamber is done differently and is more to the side of the head or to the front and is taught as a deflection or chamber.
This move was taught by Chotoku Kyan as pulling out a Jiffa. I am sure that people could assign other applications to it, but this was one of the orginal applications that were passed down that we know for sure.
As an aside, with your "Isshinryu" reference in your screen name. That is also one of the big controversies in regards to Kusanku. Chotoku Kyan taught it as a night fighting kata and Tatsuo Shimabuku taught it as a night fighting kata, yet there are many karate people out there who deny it has applications and strategies to be used at night and say that it is a myth.
Thanks for the link and info (first I've heard of jiffa used by men), but....
While Hohan and Kyan Sensei may have employed/adapted weapons to Kusanku, (Shimabuku a developed a sai version) the kata was likely designed without jiffa, sai or other weapon in mind, their use being a later thought by these great Masters. The photo you show is the move I had in mind, and if the rear hand is really drawing out a hair pin, why is the next move a kick? Where is the stab?
This rear hand (as shown in the photo) is likely in the position after a parry. That hand can now grab the attacker's wrist, and the front hand after the shuto strike (as shown in the photo) can grab the shoulder or back of neck. This is followed by a kick, plant, pivot and takedown. This is one effective and realistic application to the series of moves (as done in some styles and is consistent with Okinawan fighting doctrine.)
As for the night fighting interpretation, it made for a good story told to American soldiers who brought Isshinryu back to the USA. Framing the moon and brushing away branches in the opening move, stomping the ground to distract the opponent in the dark, dropping to the ground after the jumping crescent kick to hide in the shadows, and so on. There are more practical (and less fanciful) bunkai interpretations to these moves that can be used any time of day, IMO. This opinion is shared by some current Okinawan masters.
Suffice it to say there are many stories, versions and misinterpretations in karate due to the lack of written documentation. It is possible that the Americans who briefly studied in Okinawa (usually for less than 2 years, and don't forget, this time period was only 10-16 years after we bombed the hell out of the island and dropped a couple of atomic bombs on their mainland) were not told the true bunkai (oyo or hidden meaning) by the Chauvinistic Orientals (meant with respect).
All we can do is have an open mind, understand the history the best we can, believe what we may, stay true to practical and realistic combat principles, and love the art.