NiKi is your, or rather was your best friend. You got into a fight with him.. The cause of this fight was, that NiKi thought, that you've been talking behind his back and taht you actually just use him...

NiKi : "I thought we were friends!? I trusted you, and you just wanted to use me all along!?!? Wow! I must have been really naive, for not to notice what has been going on behind my back all this time!! Now I wish I ahd never even met you!! I hate you!!" he yelled at you, as you looked at him