This article contains major plot spoilers from the manga that have not been revealed in the anime. Proceed at your own risk.
They are good friends, apart from realizing that she is in love with Yuu, and the latter thought that Fuuka was in love with him, but this turned out not to be true, because he is not interested in girls. He was the second In joining the band, he worries about Fuuka.
They get along, and often it bothers him making him angry or embarrassed, he feels attracted to him, to Nachi at first it seems that he does not like her because it bothers him and unlike him he is bisexual. Makoto is responsible for keeping it under control when he gets angry