Usami "upgraded" to worst girl.
Using a guy who has feelings for you to stalk your love interest (who knows nothing of your feelings) and a shared friend (whom you are jealous of for getting along with your love interest, who, again, is clueless of your feelings toward him), ready at any second to sabotage any perceived "intimacy" between the two to satisfy your own raging jealousy is nothing short than the mark of a terrible personality and also a huge dick move on your part. Also, just leaving that guy there and going off on your town to stalk your crush some more is a really far cry from being nice. Shame on you, Usami.
BTW, I'm not angry or outraged or anything, just disappointed.