Dekisokonai Majo no Yomeiri: Katsute no Deshi kara Kojirase Dekiaisarete Nariagarimasu

The man who bought me at a slave auction is... my former disciple? The duke sorcerer has been in love with her for ten years! Linya is a demi-human who is unable to use magic due to one of her horns being broken. She was chased out of her homeland, the country of demi-humans, and made a living by selling potions in the humans' country. One day, Linya makes a deal with a black market salesman to buy a young slave, Gil. Gil has an enormous amount of magical power, something that's rare in humans, so Linya decides to make him her disciple. However, Gil is extremely clingy! They became unusually close, and the kiss he gave her as he transferred his magical powers to her was so sweet and passionate, it was electric. Then, three years after Linya and Gil started living together, someone appeared, looking for Gil... (Source: BisouBisou Comics)