 If you liked
Full Moon wo Sagashite
|
 ...then you might like
Ran to Haiiro no Sekai
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Both involve a young, naive, and headstrong girl who is able to transform into an older and more beautiful version of herself with certain limitations. Because the girl is so naive she gets into trouble when she is her older self and sometimes has to be saved by her male love interest. There are also much more dark and complicated side plots going on at the same time that involve supernatural beings.