Tenshi na konamaiki

Megumi-chan is a teen-aged girl with a secret past. She used to be a boy until she saved a magician from a gang of boys and was given a magical book. As a boy when he bled into the book a genie appeared to grant one wish. Megumi wished to be a man, but the genie granted the wish backwards so he turned into Megumi-kun, a girl. Years pass and Megumi grows up to be the most beautiful of girls but still acts and fights like the boy that she really is. Upon entering High School she immediately beats up the school bully who falls in love with her. Thus begins her adventures looking for that book to change her back and fighting off both admirers and her on-coming femininity.