The Transfer Student is Sailor Jupiter

Usagi is saved by a new girl in town from the bullies. When Usagi realizes the girl who saved her is at her school, she befriends her. The new girl, a tomboyish Makoto Kino, seems tough on the outside, but when she lets her guard down for a popular basketball player who turns out to be a Youma in disguise, the vulnerable Makoto must awaken as Sailor Jupiter to defeat him.