Bulgeun Jeojuui Gisanim

Ratan the mage is being pursued by the knights of the inquisition for studying the forbidden Red Curse. When he seeks refuge in The Black Forest, he runs into its deadly resident knight in steel armor who happens to be the curse's victim. Thankfully, Ratan's offer to lift the curse keeps the knight from killing him. But the solution involves some heated action in the bedroom, and Ratan isn't so sure that he'll survive to see another day...
(Source: Tappytoon)
Notes:
- Part of RIDI's Cheot XX Danpyeonseon (첫XX단편선) Collection.
- Chapter count includes three side story chapters.