With a noticeable tan and bleached hair, Momo Adachi is a high school student who is frequently misunderstood by her classmates. She's accused of being a playgirl and is the subject of many rumors, most of which originate from her ‘best friend' Sae who is jealous of Momo due to them having a crush on the same boy. Momo's life only gets worse when Kairi Okayasu, who she once saved from drowning, decides to make her his own. Kairi coming into Momo's life only encourages Sae to spread more rumors about Momo and Kairi while going after Toji herself, creating quite a complicated situation for everyone involved.
Since both series are by the same author, someone who appreciates the art style and character design of either will be happy to find that both are consistently well-drawn.
Second, both series deal with a female protagonist struggling not only to find love, but to overcome her insecurities. In Peach Girl, the heroine deals with with being tall and tanned in a world where short and pale is beautiful. In Papillon, she struggles with constant comparison to her popular twin sister.
There is also a similar story-line with the love interests. The initial guy somehow finds himself dating the cruel girl closest to our protagonist while the second fellow makes us laugh and turns out to be far smarter than even we would have guessed.