Hi again,
Interesting, and a suprisingly popular subject too, amongst us

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Sodacat, regarding the Witchblade manga (Witchblade Takeru), I have seen a few pages of the work and most of the art. Also, you do have a good point to make in its overall...artistic impression leaning to the ecchi and sometimes hentai side of things; though the story and its weight are generally quite compelling, seemingly

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Also, Mazoku, another good point. Actually, I mean any type of symbiotic entity; the suit sub-type simply being the most memorable and iconic in most genres which can be raised.
Additionally, to further extend the discussion, I have a few things that may perk interest and debate.
Firstly, I would like to raise the fairly obscure franchise "Agent" Aika
http://en.wikipedia.org/wiki/Agent_Aika . In summary, Aika is a woman who bonded with a entity and can transform with it into a far more powerful, remarkable form. Of note, regarding symbiotes in anime, this work was one of the best examples, for me personally, of the subject, before the Witchblade anime/manga. It even touched upon the idea of replicating the symbiote/entity artificially - a concept echoed in the "Clone Blade" of the Japanese Witchblade franchise.
I have included some examples of Agent Aika too, for the curious.
Aika (prior to TF - entity triggered)
http://www.animevice.com/aika-sumera...027/83-315718/
Aika (partial transformation)
http://www.animevice.com/agent-aika-.../015/83-47738/
Aika (full transformation; also called "Shivie Aika")
http://www.absoluteanime.com/aika/aika-ultranite.jpg
It is also of note that Aika's symbiote is quite particular in some ways. Mentally, their can be a merged consciousness when transformed, but also as opposed to shredding or simply assimilating her clothes, it actually disrobes her before bonding; and, in combat, can even assimilate some foreign objects into itself (admittedly on a small scale).
My second point is also a little obscure, though this may ring a few bells; as it has done for me. But, a little explanation is in order first

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Some may recall the late 90's series "Bubblegum Crisis Tokyo 2040"
http://en.wikipedia.org/wiki/Bubbleg...sis_Tokyo_2040 . Essentially, before reloading and reworking a franchise became popular, this was a reimagining of the famous cyber-punk classic "Bubblegum Crisis 2032" - the exploits of female mercenaries in a dystopian Tokyo with powered armour (Hardsuits).
This newer series sticks close to the original material, though the final episode has something of note. As the Hardsuits in this series are techno-organic in nature, there is an incidence where a protagonist's (Priss Asagiri
http://www.animevice.com/priss-asagi...110/83-147689/ ) armour begins to mutate; notably with her inside and against her will.
This process conflates the powered armour, symbiote and posession genres as the armour transforms into a more organic, bestial form and seemingly posesses her too; though due to the nature of the suits, it may just be a expression of her anger and rage during the episode.
The episode can be seen here:
(unfortunately, this may be limited in where you can view it).
The first change begins around 01:35. The Possession continues about 03:55 and the reversion can be found around 06:30.
These times are approximations gained from another version, but the scenes can be seen if the episode is simply watched through as well

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In all, this particular change was one that had escaped recollection for a few years, but recalling now, it is quite remarkable in the impression it leaves; especially the sense of struggle and physicallity.
Thanks,
Alchemical Night.