Tenshi na Konamaiki

Megumi Amatsuka, a rough and tumble nine-year-old boy, always dreamt of becoming the "manliest man on earth." Upon receiving a book of magic from a sorcerer whom he saved from a group of local thugs, Megumi summons a genie in order to make a wish. But due to a sick twist of fate, the genie turns out to be an evil one, and Megumi winds up being the "womanliest woman on earth"! Six years later... Megumi is the most desirable girl in school, but deep within her hot-mama facade is the same trash-talkin,' punk-stompin' boy.

(Source: VIZ)