This is an ambiguous merging of the non-consensual and the consensual form of sexual slavery, which is often depicted within nukige.
Although some means of force is applied to some unwilling people like in non-consensual sexual slavery, the border to consensual slavery is blurry to the most.

In the exaggeration of this medium, the unwillingness transforms rather instantly by means of sexual stimulation to a (semi-)consensual form.
This unnatural behaviour of characters is pure fictitious and one feature of nukige.
Further, this depiction of sexual slavery borrows regularly the symbols by which a consensual submission is demonstrated of the submissive to others indicating the belonging to the dominant, such as wearing a collar, special tattoos, piercings, a very short haircut or a bald head.

Therefore, a nukige with sexual slavery as theme defies often a clear classification into one of the two real life forms of sexual slavery.

IMPORTANT NOTE: This variation of sexual slavery starts out as non consensual and either turns consensual by bringing out the victim's inner masochist or mindbreak erases most of the victim's original personality to the point, where one cannot really talk about "will" and "consensuality".