Sachi is 17 and has never had a boyfriend, so she goes to a goukon (dating party) with her friends, where she meets Yuki, who claims to be awkward with girls, who he doesn't spend much time with, going to an all-boys school. The next day, her friend Akemi tells her that Yuki is a playboy who uses girls. Sachi decides to follow Akemi's advice about Yuki, but ends up running into him several times.
Unlike most shoujo, it isn't clear from the start that Yuki will mend his bad boy ways and he and Sachi will sail off into the figurative sunset after a few angsty bumps, but it's less clear here. Yuki (who really isn't much of a bad boy, though he does try at times) is very much in love with someone else, a relationship that ends up affecting pretty much every character, and carries an enormous-and not always emotionally healthy-baggage, and after a couple volume, it seems Sachi might be much better off with Yuki's friend, Akahoshi (Who is something of a tsundere and prone to snarking. One of my favorite things in the series is when he gets upset because Sachi doesn't snark back at him, but instead ends up with important realizations or going off to have deep thinky thoughts.)
I will spoi that everything works out largely satisfyingly, though I spent many chapters going "Everyone likes/is with the wrong person! Fix it!" without really being quite sure how I thought things should be. (If shoujo series got fandoms the way shounen series tend to, the fandom for this series likely would have been...very dramatic. Though apparently the fan letters Karuho got had some drama.)
While Kimi Ni Todoke often relies of misunderstandings and lack of communication for conflict (Well, in earlier volumes. Less so once volumes reach the double digits.) Crazy For You has complicated and messy relationships, and all the drama that goes with them, thought how the problems are dealt with is sometimes similar. Sachi is also at the complete opposite end of the spectrum from Sawako, and a character I feel would normally be a supporting character. she has curly hair, is actively seeking a boyfriend, prone to gullibility, and endlessly cheerful and energetic, which is a type I feel is usually reserved for the shoujo heroine's friends, not the heroine herself. (Not that Sawako is particularly conventional heroine herself, though I feel she's closer to it than Sachi, once you strip away the "looks like the girl from The Ring!" element.
Unrelated note: I am traveling a lot this weekend and so reading a lot of manga in the car. I am also testing how I do with regular interneting with only my tablet for a couple days, before doing it for a whole week come WisCon. Utterly random words are likely cases of my not catching autocorrect doing things like changing "manga" to "manta," and I'm sure I missed even more typos than usual.