Sweet Punishment -I'm the Guard's Personal Pet-

The story is set in a prison in the near future year of "20XX." It revolves around Hina Saotome — an office lady imprisoned despite her innocence — and the elegant yet sadistic guard Aki Myojin. Hina's heart and body are at the mercy of Myojin's "cruel yet sweet domination" from physical examinations to even her lover's prison visits.

(Source: Anime News Network)