To say that Flash isn't a character is silly. It also seems that you're implying that the only way he could actually have any personality is if he was a genius or something, as if guitar playing nice guys don't exist anywhere in the world, I'm a guitar playing nice guy IRL. Also, you say that the only way the love interest would've made sense is if they had any common ground to start on. Not many high school relationships are based on common ground, hell, not even many adult relationships are. Think about any TV show or movie with a love interest. About how many of those started with nothing more than a look in the eyes, before the characters get to know each other? Im gonnasay quite a few of them