The relationship between the first-year and third-year players of Karasuno High School volleyball team evolves throughout the series "Haikyuu!!" as they spend more time together practicing, playing matches, and facing challenges as a team. Initially, there might be some tension or misunderstandings between the younger and older players, but as they work together towards their common goal of winning games and improving as a team, they start to understand and appreciate each other's strengths and value each other's contributions to the team. Over time, they develop a strong bond and sense of camaraderie that helps them overcome obstacles both on and off the court. The first-year players look up to the third-years for their experience and leadership, while the third-years guide and support the younger players in their journey to become a stronger team. This dynamic relationship plays a significant role in shaping the team's growth and success throughout the series.