If Kageyama had stayed at Kitagawa Daiichi instead of transferring to Karasuno, the series "Haikyuu!!" would have taken a different direction. Without Kageyama joining Karasuno, the dynamic of the team would have been altered, affecting the strategies and gameplay of both Karasuno and other teams they faced. Kageyama's growth and development as a setter, as well as his relationships with other characters like Hinata, would have been vastly different. This change could have led to new storylines, rivalries, and outcomes in matches throughout the series.