I would be angry and upset! The things you describe (new friend, talking excitedly, secretive, taking an interest in appearance) are regularly identified as behaviour associated with cheating.
I would probably show up to coffee if it's just coffee between friends as he is trying to make out! Then depending on his reaction, I'd either ask him to stop like he said he would and if the reaction was over the top-I wouldn't give him the choice!
Hugs OP xx