It all started during their childhood. Ever since then, Kuroo was incredibly mindful of Kenma's quiet, withdrawn personality and had the sense to not drag him out to do something that he didn't have any fun in doing.

Then Kuroo saw Kenma's interest in volleyball tactics, so he urged him to become a setter, citing it as a perfect position for a strategist and not having to move around that much.

Later, Kuroo convinced Kenma to join their junior high's volleyball team and they have played volleyball together since then.

During Kenma's first year of high school, he had trouble fitting into the team but Kuroo encouraged him to stay by telling him that he is a big asset to the team.

By that time, Kuroo definitely had it in mind that once he became the captain, he will have to make an effort for the members to get along with Kenma.