Iwaizumi doesnt have anger issues. He just like to show his friends that he loves them enough to be like Americans friends. Oikawa and Iwaizumi has been friends since basically birth. Before you go and say that hes abusive to Oikawa or try to say hes only doing it bc of what happens in timeskips. Just know that i would like you to shut up. Me and my family are like Oikawa and Iwaizumi, at this point its like where friends instead of family. It even says that he is one of a few people who know when oikawa is faking happiness. To be honest, think to yourself if you know someone who asks like an haikyuu character, cannon, if so make your headcannons about that not what you think just based on looks and what they say.