Kain is a calm, sometimes sarcastic young man, driven by his dream of following his father's footsteps of becoming a Dragoon and shunning the King of Baron's wish for Kain to follow Cecil's profession of a Dark Knight. He has been friends with Cecil and Rosa since they were young, but their relationship is strained by their rivalry as soldiers and their love for the same woman, although Kain hides his feelings.

Kain's personality changes when he is possessed by Golbez, becoming cold towards Cecil, though his love for Rosa still shows. Once freed from Golbez's control, Kain is forgiven by Cecil and vows to atone for his past actions, a promise that carries over into The After Years, as he tries to vanquish his dark side and helps Cecil's son Ceodore.

Kain was born in Baron to the Commander of the Dragoons, Ricard Highwind. His father was particularly active, but died while Kain was still young, sprouting rumors that he may have been assassinated. In The After Years, Kain recounts that he used to hate his father for how strict he was. Kain was raised with Cecil by the King of Baron.

Initially, Kain disliked Cecil, since the king treated Cecil more like a son than Kain. It was often Rosa who would stop the two from fighting. The three became friends, and Kain became Cecil's rival and developed romantic feelings for Rosa, although she and Cecil were likewise enamored.

The king wanted Kain to become a Dark Knight like Cecil, but Kain wished to follow in his father's footsteps down the path of the Dragoon to defend the Baron Castle. Kain cared for his father's dragon, who grew weak but still faithfully awaited his master's return. The Dragoons were on the verge of disbanding after Kain's father's death, but reformed when they saw the devotion of both the dragon and Kain. Kain was appointed the Commander of the Dragoons. The fate of the dragon is unspecified, but it does not appear in any version of Final Fantasy IV.