Probed

Rick is fighting the good fight—rebelling against the aliens who’ve invaded Earth. But when his mission goes awry, he finds himself captive to the very tentacled monster he’d planned to assassinate.
Most Supreme Specimen, as the alien insists on being called, claims he’s caring for Rick, that the invasive probing he regularly subjects Rick to is intended to ensure his good health, both mentally and physically, but Rick isn’t buying it. The aliens are evil, especially this one, and escape is necessary.
Right after this next probing…
Content contains instances of dubious consent and light medical kink