Anno Moyoco was Okazaki's assistant and helped complete Helter Skelter after Okazaki was physically unable. Her strong influence on Anno, in both the drawing and writing style, is immediately evident. The themes are similar as well—women struggle with their own body image, how others perceive them, and the destructive extremes they go to for appearances.
In both stories the MC blames her appearance for her current situation and tries to become more beautiful at all cost to improve her social life and career as well as to gain happiness. Furthermore both titles share the josei and psychological genre and are quite short.
Both have the main heroine who is struggling with her weight. Though maybe Cousin is not as sad as the Shibo Toiu Na No Fuku Wo Kite, they both make you think about values and whenever is the ouside so important.