Bondage/BDSM/Kidnap or Confined

Sadistic and cruel confinement.

Russian and Korean spy. One gets captured eventually.

CSI op captured by the mafia dom he is tracking

Trauma driven college student kidnaps another college student and keeps him confined, chained, and restricted in his house. Turns out there is a traumatic backstory behind both of them.

MC escapes his destructive father but his half-brother comes after him years later to bring him back to "paradise"

One MC is kidnapped after he traumatized the other as a teen. The traumatized gets revenge as an adult. Dog Cage.

The gardener cares for him as a child and he grows up loving the gardener. But when the gardener wants to leave 10 years later, he doesn't like that and makes a rash decision.

College sub with dom professor pulls in another college student who has a crush on the college sub.

Guideverse. A mutant Guide is found by a S level Esper. S level decides Guide belongs to him and keeps him against his will.