Jinenji is a half-human, half-horse demon residing in a hut with his human mother. They cultivate various medicinal plants in the field he inherited from his demon father. Some of these plants are renowned for their potency against poisons. Jinenji first appears in episode 31 of the anime when Kirara is poisoned by Naraku's shoki. Kagome and InuYasha journey to the village seeking a cure. Upon meeting Jinenji, they discover he is a gentle giant initially frightened of humans due to mistreatment by villagers who wrongly blame him for deaths purely based on his demon heritage. When they find him, they help clear his name. His arms bear scars from attacks.
Upon encountering Kagome, he is surprised she shows no fear of his appearance and willingly aids him in gathering herbs. InuYasha, having faced abuse from humans as a child, tries to persuade Jinenji to be more assertive towards the villagers, especially after he rescues them from a demon. Ultimately, Jinenji opts to maintain his gentle demeanor, providing injured villagers with healing herbs. Out of guilt for their prior mistreatment, the villagers assist Jinenji and his mother in rebuilding their burned-down hut and cleaning the herb field.
Once a month, Jinenji becomes fully human during the day, unlike InuYasha who turns human at night. He hides away in the hut under a blanket on these days, likely known only to his mother. It seems he transforms into a larger-than-average human. During one such transformation, Rin visits seeking a cure for Jaken, poisoned while protecting her. Jinenji is immensely strong, supporting substantial muscle mass, but his unique demon ability amplifies his strength further. Activating this power makes his body glow blue, enabling him to decapitate a large demon by squeezing its neck and destroy its head with a single punch.
In the final episode of InuYasha: The Final Act, Jinenji is last seen helping Kagome select plants to make potions.
