The reason why this man approaches Othello's home is that he was about to accuse him in stealing Barbantio's daughter. This conflict was set up because of Iago which can describe his character as a two faced liar that (even though he is such a liar) he reveals his sward in order to help Othello in this fight. And what about Othello, I would say that he is his stoic self.
Hope that will help you!