Honestly i dont think natsuki has the right to be this upset, so far shes only been meddling on the sideline. And yeah shes (probably) given up on her crush for the sake of her friend but thats her choice and she should be able to respect their boundaries and the fact that koichi is anxious.
Anyways, weve finally gotten to the ending that was clear since the firework chapter or maybe even before, yay ig