Hyakusou no Uraniwa

Once upon a time, Marcel’s sister fell in the forest while gathering herbs. Her injuries were grave and Marcel was at a loss for what to do, until a fearsome horned man appeared, offering help–in exchange for a promise. Now, ten years later, Marcel returns to the woods, steeling himself for death. Instead, he finds something quite different: a gentle soul, friendship…and perhaps something more.
(Source: Seven Seas Entertainment)
Note: Includes the one-shots "stalks", "passage", and "Shinshoku (侵食, Corrosion)", two chapters of "Tabi no Tochuu (旅の途中, Along the Way)", and one extra chapter.