How is blond girl a good girl? We know nothing of her, only that she missed her opportunities and that she is in love with him?
And this is phenomenally played by author-san. We know not what She is capable of, nor do we know what bothers him.
Author-san knows how to subvert expectations and how to build-up tension by keeping things a mystery.
And the webmanga Format is best suited for his intentions. How many times do you read pixiv Mangas that are lifeless and not thought trough well? A lot of course.