Akane Tendo is the main love interest of Ranma Saotome and several characters in the manga and anime Ranma ½.
Biography
Akane is the youngest daughter of the Dojo Tendo at age 16. She's frequently the target of all the boys in school who try to beat her in hand-to-hand combat in the hopes of earning her recognition and love. So far only Ranma has succeeded. Unlike all the other girls her age, Akane isn't interested in boys, believing they'll hold her back.
Romances
Ranma Saotome
When Ranma first met Akane he was in his female form. Akane took a liking to girl Ranma and said they could be friends. When Ranma took a hot bath and turned back into a boy, Akane's opinion of him completely changed and they've been acting hostile towards each other ever since. Her family chose her to be engaged to him and carry on the Tendo family dojo. After becoming further upset by his insults, their engagement was not off to a good start. With time, both Akane and her relationship with Ranma mellow out. There are hints that the two might love each other more than they'd like to admit. One example is when Akane's hair was chopped off, Ranma told her she looked prettier with short hair and she kept it that length.
Ryoga Hibiki
Ryoga travelled to Tokyo to fight with his long-time rival Ranma. When he's cursed with the ability to turn into a pig when doused with cold water, Akane takes him in without realising who he really is. Ryoga then develops a crush on Akane, giving him even more reason to resent Ranma. Ironically, Ryoga is one of the few people Ranma is openly friendly towards. Eventually Ryoga gets over Akane and starts dating a pig-breeding girl by the name of Akari.
Tatewaki Kuno
Kuno is the upper classman and a Kendo practitioner. His attraction to Akane borders on obsession, rivalled only by Ranma's female form. Like all the other schoolboys, Kuno frequently challenges Akane to sparring matches, saying that if she wins then she can date him as a prize, thus not putting any real effort into their matches.
Hikaru Gosunkugi
Hikaru is a creepy classmate of Akane's with an obsession with voodoo. Since he's one of the few male characters with no martial arts training, his attempts to woo Akane fail instantly.
Love Rivals
Despite refusing to admit any feelings towards Ranma, Akane stil shows signs of jealousy whenever she sees a girl who finds him attractive. This is a source of frustration to Ranma, her family and generally anyone who knows her.
Shampoo
Shampoo (or Xían Pu, depending on how you spell it) is a Chinese Amazon that Ranma beat in hand-to-hand combat. Her culture dictates that any Amazon who is beaten by a man must marry him, leading to several confrontations where Shampoo tries to seduce Ranma.
Ukyo Kuonji
Ukyo is Ranma's childhood friend and an okonomyaki chef. Growing up, Ranma used to believe Ukyo was a boy due to the way she dressed. It wasn't until they were both 16 that she revealed her gender as well as her intentions to marry Ranma. Unlike Shampoo and Kodachi, Ukyo isn't nearly as hostile in her attempts to get to Ranma, as he seems to like her enough as a friend and presumably only needs gentle prodding to turn those friendly feelings into romantic ones.
Kodachi Kuno
Kuno's sister Kodachi is attracted to Ranma's male form in a similar way that Kuno himself is attracted to Ranma's female form. She's a gymnast and a narcissist, only persuing Ranma because of his looks and not caring about his well-being. Her hostility towards Akane and Ranma's other suitors is much more vitriolic, frequently using underhanded tactics to get what she wants.