Sugar Doll is Kusumi Koharu's fourth and last solo photobook. It was released in September 27, 2009. The photobook was published by WaniBooks and also came with a Making-of DVD. The photography was done by Nishida Kouki. The ebook edition of the photobook was released on July 29, 2013. The title of the photobook describes Kusumi's sweet charm and anime doll-like qualities.