Melmo gets a magical bottle of candy from God—blue pills age her up to 19, red ones turn her back into a kid, and mixing them creates some weird effects (fetus form, then she can turn into any animal she wants). The catch is her clothes don't scale with her transformations, so she either ends up shredded or bursting out of children's sizes in her adult form.
She's fundamentally good-natured but constantly caught between what she actually is and what her older self wants. When she's 19, she's genuinely beautiful, and guys tend to fall for her pretty hard—though the whole situation's complicated by the fact that she's still mentally a kid most of the time.
Content compiled by AnimeList.moe from publicly available sources.
