WHO THE HELL IS RIN!?!?

Isuzu Sohma, also called Rin Sohma, is one of the two Zodiac members met only in the manga. She is the Horse of the Zodiac. She has long black hair, but it is cut later on, and goes to the same school as Kagura, as does she live with Kagura's family because her own family abandoned her. She is fairly cold due to the fact that her parents rejected her. She and Hatsuharu dated for a while in secret until Akito found out and pushed her out a second story window. The only witness to this happening was Hiro. After that, she was hospitalized for a while. While in the hospital, she broke up with Haru so Akito wouldn't get mad again. She is a prominent character toward the end, trying to find a way to break the Zodiac curse in every way she can. She gets convinced that Ren Sohma, Akito's mother, knows how to break the curse. Ren tells Rin to steal a box from Akito and in exchange she'd give Rin the key to breaking the curse. But Ren lied, and Akito caught Rin in her- wait, you haven't read the manga- his room. Akito locked Rin in the Cat's Room (the room Kyo is supposed to go into for the rest of his life after high school unless he beats Yuki) and cuts her long hair. Tohru considers Rin a friend, although Rin doesn't seem to feel the same way for a while. In the end, Rin ends up back together with Haru.

In short: Read the manga. If not online, go find the books in a library or a bookstore.

link

She is the horse of the zodiac here is a link:
link
if that doesn't work type in www.mangareader.net and that website should come up then search fruits basket (on the website). She doesn't show up at the start of the manga, just letting you know :) You will also come across the rooster the other zodiac member not mentioned in the anime, I can't remember his name though. Happy reading :)