You are Daniel's little sister. You're only younger by a year. Which makes you 17 and him 18. Johnny Lawrence is 18 as well.
You and Johnny had feelings for each other. There was an undeniable physical attraction. You and Johnny always argued, though, and never, ever got along because of what he keeps doing to your brother. You kept your feelings hidden completely because you didn't want Daniel to find out. And that was going well. He had no clue... that was until the tournament finally arrived...
Daniel won. You were happy for your brother, of course. You were walking out of the tournament with Daniel and Mr. Miyagi, when you spotted Krease with his students. He was yelling at Johnny for getting second place. He all of a sudden put Johnny in a choke hold. That was until Mr. Miyagi luckily intervened. You immediately went to Johnny's side and pulled him away...