The relationship between Yoichi Isagi and Meguru Bachira in the manga "Blue Lock" starts off with them being teammates who initially have different playing styles and attitudes towards soccer. As they train together and face various challenges in the Blue Lock program, they begin to understand and respect each other's strengths and weaknesses. Their bond strengthens as they work towards a common goal, leading to a deep friendship built on trust, teamwork, and mutual growth as players.