Saki Hasemi is a Japanese anime screenwriter and manga writer, best known as the original creator of the long-running To Love Ru franchise. Born on October 25 in Chiba Prefecture, Hasemi is male despite the feminine given name. His career began in the video game industry during the 1980s and 1990s, where he worked on character design, planning, and scenario writing for various titles including Zero4 Champ, Mini 4 Boy, and Little Busters Q.

Hasemi transitioned into anime screenwriting in the 2000s, contributing scripts for series such as Sugar Sugar Rune, the 2005 adaptation of Black Cat, Powerpuff Girls Z, and Moetan, where he also handled series composition. His professional relationship with manga artist Kentaro Yabuki began during preliminary meetings for the Black Cat anime adaptation. When Hasemi expressed interest in writing an original manga, Yabuki later reached out to propose a collaboration. This partnership resulted in To Love Ru, which was serialized in Weekly Shonen Jump from April 2006 to August 2009. Hasemi served as the story writer while Yabuki provided the illustrations. The series follows high school student Rito Yuuki, whose life becomes complicated when he accidentally becomes engaged to Lala, the alien princess of the planet Deviluke. The title combines the English loan words for trouble and love, reflecting the series harem romantic comedy nature with science fiction elements.

A direct sequel, To Love Ru Darkness, was serialized in Jump Square from October 2010 to March 2017, again with Hasemi as writer and Yabuki as illustrator. This sequel shifted focus to Lala younger sister Momo and her plan to build a harem around Rito. Together, the two manga series have over 16 million copies in circulation. The franchise received multiple anime adaptations, including the 2008 television series, six original video animation episodes, the 2010 second season titled Motto To Love Ru, the 2012 To Love Ru Darkness television series, and To Love Ru Darkness 2nd in 2015. Hasemi is consistently credited as the original creator across all these productions.

Beyond the To Love Ru franchise, Hasemi collaborated with artist Kotaro Shono on the manga Star + One! from 2013 to 2014. In November 2020, he launched a new manga series titled GT-giRl with artist Wise Speak in ASCII Media Works Dengeki Maoh magazine. Hasemi work is characterized by romantic comedy narratives that test the boundaries of fan service acceptable in shonen manga, a direction he and Yabuki deliberately explored. His significance in the industry stems primarily from the commercial success and cultural longevity of the To Love Ru franchise, which remains one of the most recognized harem series in modern Japanese manga and anime.