The Crown Prince of the Neighbouring Kingdom Was Being Sold as a Slave, So I Bought HimNewRingoku no Outaishi ga Dorei Toshite Urareteita node Katte Mimashita; 隣国の王太子が奴隷として売られていたので買ってみました

Natalie, one of the candidates for the Great Saintess, is framed and condemned by her rival Florancia during the Great Saintess Selection Ceremony. Cursed to die the moment her divine power runs out, she awakens to her Great Saintly powers at the last moment and escapes with her life. Heading to a trading post to hire a bodyguard in order to escape abroad, she finds that Prince Vincent of a neighboring country is being sold there. Although it smells like trouble, she decides to buy him because of his high combat ability and, more importantly, the ulterior motive of "maybe I'll be protected in the neighboring country if I help him?" However, after the purchase, a shocking truth is revealed. "Vincent... weren't you meant for gladiatorial combat!?" Vincent's markings are a bizarre design that causes him to suffer pain if he doesn't sexually satisfy his master. To alleviate his suffering, Natalie is forced to receive "service" from the proud Crown Prince...!? Natalie is supposed to be the master, but before she knows it, she's being manipulated by Vincent in this role-reversal, obsessive love fantasy!