Seeing Totoku Hiyoshi No Kamae for the first time can be misleading.  Usually a student's first exposure to this kamae is seeing someone hold a sword out in front of themselves while someone else throws shuriken at them.  Then the instructor hands the sword to you and says, "Next."

by eflon

This aspect of Totoku is often perceived as one of those quirky things in our training that we may try out, but never take seriously.  After all, who has had to dodge shuriken for real?  I'm not counting the dishes your girlfriend threw at you during a recent argument.  Maybe you try this out, maybe block a few rubber shuriken and then forget it.

Totoku forms part of some very rich strategy in our art.  And the more you look for it, the more you will encounter.  I personally have heard Hatsumi Sensei reference it many times, and it wasn't anything to do with shuriken blocking.  It is a running theme in our taijutsu that has to be experienced from a qualified teacher.

Maybe a starting place to understand this kamae can be from the Tachi.  This sword was mainly held in one hand.  There was little tradition of handheld shields in Japanese Budo.  So how do you deal with incoming arrows, spears, or enemy sword attacks?  You use your own sword.  The first use of the sword is to protect yourself before cutting.  It becomes your first line of defense and your shield.

What if you don't have a sword?  The idea of Totoku goes even deeper.  It moves into the idea of hiding yourself behind a shield.  But what is a shield?  Soke speaks about this in reference to Goton No Jutsu:

Examine the character for "Ton" as used above in Tongyo ("hiding one's form"; or alternatively, "the discretion doctrine"), and you can discover it to be a combination of the characters "fleeing" with a "shield" - just as along the path of Ninpo.  The priciple of recognizing the value gained by winning through flight is one of Ninjutsu's cardinal rules.  However it is not simply a question of escaping.  What can one use as a shield?  One can use:

• the Five Elements (wood, fire, earth, metal, and water)
• the Five Rings
• the Five Ways (the way of enlightenment)
• the Five Arts
• the Five Teachings
• the Five Confucian Virtues (benevolence, rightousness, prosperity, wisdom, and sincerity)
• Nature
• the shining (or shadowed) glory of the martial ways
• beliefs
• politics (or rather policies for life)

the shields are multiple and varied.

Soke says on another occasion,

Everything is a natural shield.  So, anything can be a natural shield.  One should move in a connected way like Juppo Sessho, and Koteki Ryoda which include these teachings.  Such things are written in old Japanese scrolls.

And finally, I watched one day as Soke was demonstrating some of his mysterious muto dori, and he explained, "You must evade by the thickness of air.  Use the air as your shield."