It's OK.  They are not sex slaves.

Behind Illicit Massage Parlors Lie a Vast Crime Network and Modern Indentured Servitude

https://www.nytimes.com/2019/03/02/us/massage-parlors-human-trafficking.html

Curious that the NYT uses indentured in this case but sex slaves in the "comfort women" case.  Yet another instance of the NYT having one standard for Japan and another for predominantly white countries?

In point of fact a large fraction of "comfort women" and prostitutes in general in the Japanese empire were in fact indentured, typically to secure funds for their families.