「Rod within captive, captured prey」and so many other combinations all depict CAUSE, CAUSATION, DEPEND ON, IS BASED UPON, A MEANS TO AN END, DEPENDENT and so on that underscore the keeping of sex slaves in a personal harem, and likely need no further explanation. Other possibilities depict the one with the rod being DEPENDENT UPON all the MANY GRAND ORIFICES that have been captured for playful use, whenever the need arises. Sex slaves are DEPENDENT upon the owner/master for sustenance, but the master also is dependent upon the slave as a MEANS TO AN END (or, backside if you prefer), particularly if only「one captured slave」is kept. And a「captive rod」suggests a sexual DEPENDENCY of various types, as well as the root CAUSE for all sorts of behavior and REASONS for misbehavior.
　「Both hands captured, enclosed」equates to the English 'my hands are tied' as the CAUSE for DEPENDING upon someone else to do something, for help, or to solve a problem.
　「Enclosed with a taut hand」(male), or,「hand taut in orifice」(female) are conditions nearly all humans DEPEND UPON from time to time to CAUSE a desired result in order to relieve internal stress and pressure autoerotically. Obviously, anyone who becomes「enclosed」or「captured, confined」and alone as only「one enclosed person」DEPENDS UPON, is CAUSED to use his or her「own two hands」for that matter. The REASON FOR using hands is because of one's solitary confinement and having no access to anyone else…a guard or two might be somewhat friendly, but not likely to reciprocate any favors, particularly if the reason for captivity is a pandemic viral infection. Notably, medical professionals the world over are currently recommending this very sort of sexual release during the COrona VIrus Disease of 2019, COVID-19.

Modern definitions (that generally disregard history) …excluding politically incorrect concepts and other meanings deemed offensive today; may list only pigeonholed definitions, euphemisms, or meaningless mnemonics)
Chinese: cause; reason; because
Japanese: cause, factor, basis of one's argument, reason, significance, something to rely on, aid, clue, way, means, to be due to, to be caused by, to depend on, to turn on, to be based on, to come from, therefore, consequently, accordingly, because of, by the way, in this connection, incidentally, in passing, as such, for that reason, depends on, to give rise to
Unihan extended: cause, reason; by; because (of)
EDRDG: cause; factor; be associated with; depend on; be limited to

Used within names (nanori)
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