Natsumi Iwasaki is a Japanese writer best known as the author of the 2009 novel "Moshidora," which spawned a successful multimedia franchise including a manga adaptation, an anime television series, and a live-action film. Iwasaki was born in 1968 in Tokyo, Japan, and is a graduate of the architecture department of the Tokyo University of the Arts. Before becoming a novelist, he studied under lyricist and producer Yasushi Akimoto and worked as a broadcast writer for popular television programs. He was also involved in the production of the idol group AKB48.

Iwasaki is the creator of the original work "Moshidora," an abbreviated title for "Moshi Kōkō Yakyū no Joshi Manager ga Drucker no 'Management' o Yondara" (What If the Female Manager of a High School Baseball Team Read Drucker's 'Management'?). The novel follows a high school girl who becomes the manager of a baseball team and applies the principles of Peter Drucker's business management text to lead her dispirited team to the national championships. The novel was published by Diamondosha on December 4, 2009. It was a massive commercial success, selling over 1.8 million copies in its first year and becoming the bestselling novel in Japan in 2010. The book has sold more than 2 million copies.

The success of the novel led to a manga adaptation. It began serialization in Shueisha's seinen manga magazine Super Jump on December 22, 2010. After Super Jump ceased publication, the manga was moved to Grand Jump Premium. The series was compiled into three tankōbon volumes. The story was also adapted into a 10-episode anime television series. Produced by Production I.G and directed by Takayuki Hamana, the anime aired on the NHK network between April 25 and May 6, 2011. Its original broadcast was delayed due to the 2011 Tōhoku earthquake and tsunami. A live-action film adaptation, starring Atsuko Maeda in the lead role, was released in Japanese theaters on June 4, 2011.

Beyond "Moshidora," Iwasaki has authored other books, including "Ace no Keifu" (The Genealogy of Aces), "Shousetsu no Yomikata no Kyoukasho" (A Textbook on How to Read a Novel), and "Kyousou Shikou". He has also served as an outside director for Iwasaki Shoten, a children's book publishing company founded by his grandfather. Through his work, particularly "Moshidora," Natsumi Iwasaki created a notable cross-media property that demonstrated the commercial potential of a novel blending sports, management theory, and youth drama, leading to successful adaptations in manga, anime, and film.