Reasons someone might have Rin and Sesshomaru as their favorite characters:
• Both show tremendous growth: Their personalities evolve considerably over the course of series.
• Complex relationship: The dynamic between Sesshomaru and Rin as well as the development of his protective feelings towards her as time progresses is emotionally rewarding for many readers.
• Individual development: They display significant changes throughout the storyline rather than staying stagnant character-wise and are given compelling storylines to help drive the events of the manga forward. Additionally, Rin develops from helplessness to becoming self-sufficient character who stands on her own and proves helpful at crucial moments .
• Unique abilities: Both possess unique strengths: Sesshomaru is a demon lord with remarkable powers whereas Rin has the special healing talent.