I've come to think that Kitamura's whole intention of becoming friends with Taiga, and not going out with her is to make her act more natural(will it EVER happen
?). Looking at his adoration of the student council president, i think he really goes for that aggressive, tough personality. However, since he noticed that she acts natural with Ryuuji, and not with him, he figured being friends and starting from that angle would eventually allow her to express herself naturally around him. IF it ever happens(I doubt it), he would then, perhaps, make a decision about Taiga.