You already told me once the symbolic meaning of Yin and Yang. So forget that for now, we'll go back to it in the future. Tell me what Yang is in the RP. How does it relate to your biography's Wood Release? How does it relate to Medical Ninjutsu?
Yin is the diametric opposite of Yang. It embodies concepts such as spirituality, the mind, creativity and/or the imagination. Going back to my example of how any physical action produces physical energy, any action of the mind produces spiritual energy. Yin Release is the capacity to harness that energy. Because of those roots, all Yin Release techniques manipulate the spirit, or the mind, in some way. Or at least, they rely on that connection to produce an effect. Take Hungry Ghost, which produces a spiritual tether to an enemy and weakens them through that tether. Or Hands of Sloth, which slowly weakens and eventually seals away an opponent's mind, the central domain of their spirit in a sense. On the note of spiritual/mental subversion, Yin Release also has a connection to Genjutsu. Illusions bolstered by Yin Release are generally far more potent than ordinary Genjutsu, since the field allows for more direct manipulation of an opponent's mind/spirit, as well as just the potency of Yin Release chakra. Such Genjutsu can break through passive defences or immunities, and can even lock off particular methods of Genjutsu break.
I don't think any Yin techniques outwardly describe the nature of spiritual energy in terms of its basic characteristics, but if I had to attribute any to them, it would be that it's cold. Opposite of Yang and all.
Back to its effects though, the last of them being related to Yin as a domain of the imagination. There are a few techniques which take advantage of this characteristic, one of them being Yin-Yang Release. The first two are Change into Heaven and Great Phantom Dragons. Both of these techniques entail the use of Yin Release to alter the physical characteristics of a technique according to their imagination. In the case of CiH, it's a targeted use, whereas the Phantom Dragons themselves are the object of alteration. A key difference between them is that CiH cannot change the fundamental nature of a technique, only its physical properties (such as turning energy solid), while the Phantom Dragons can be turned from constructs of spiritual energy into different elements that the user knows. The last technique, Creation of all Things, probably best embodies the use of Yin Release as a conduit for the user's imagination, as it involves the application of Yin Release to create a physical object that possesses whatever characteristics one so desires.
That should be it. Besides the ability to absorb/siphon chakra, which is a property unique to Hungry Ghost and Phantom Dragons.
(Inton: Ten ni Henkō) – Yin Release: Change into Heaven
Chakra: N/A (+50 chakra cost to applied technique)
Description: The user manipulates a technique of the basic 5 elements with Yin natured energy, allowing the user to change its properties. Fire can become solid, lightning can become tangible. The possibilities are as endless as the user’s own imagination. The end result is a technique neutral to all basic elemental natures. This technique is applied within the same timeframe as the technique it is applied to. The infused chakra increases the technique by an additional ten chakra, of the fifty it costs in total.
Note: Yin Release specialists can apply this technique to advanced fields, CE, and advanced elements.
Note: Using Change into Heaven to transform the inherent nature of an element does not modify its base speed.
Note: Usable 3 times per battle and 6 times per arc.
Good segue. What's the wildest application you can think of with this technique that would still be considered valid?
Honestly, I have some trouble imagining that. My answer would probably be along the lines of Kyoka Suigetsu's hypnotic abilities from Bleach. You could alter a technique's 'properties' such that they no longer visually resemble what they were created as. For example, changing a fly into a dragon, or a swamp to resemble the ground that originally occupied the space where it was made. That's the best I can come up with before I just confuse or trip over myself trying to stretch the limits of my imagination just short of the point of lunacy.