Nanaki Nanao is a Japanese manga artist best known as the creator of the fantasy series Helck, which received an anime television adaptation that aired in 2023. Nanao's professional career began with recognition in the early 2010s, including having a work pass the first selection round of the New Century Shonen Sunday Comic Grand Prix in 2013. The breakthrough came with Helck, which was submitted to a serialization tournament on the Ura Sunday website. After placing second in the competition, the series was greenlit for serialization by the publisher Shogakukan.

Helck was serialized on Shogakukan's Ura Sunday website and the MangaONE app from May 2014 to December 2017, with its chapters collected into twelve tankobon volumes. The story follows a powerful human hero who enters a tournament to become the next Demon Lord, claiming to despise his own kind, while a demon official suspects him of being a saboteur. An anime television series adaptation produced by the studio Satelight aired for twenty-four episodes from July to December 2023.

Prior to Helck, Nanao created several other works under the name N-nanaki on the platform Nico Nico Seiga. These include TIADIUM, which ran from March to April 2012, and ACARIA, which began serialization in October 2012 and was later revised and continued on Ura Sunday from December 2018 to March 2019. Following the conclusion of Helck, Nanao published a short spin-off manga titled Piwi: Fushigi na Ikimono, which was serialized on MangaONE from July to October 2018 and later collected into a single volume. In August 2020, Nanao began serializing Völundio: Divergent Sword Saga, a related manga set in the same world as Helck, which remains ongoing.

Recurring elements in Nanao's work include fantasy settings that explore conflicts between different races or factions, such as humans and demons. The stories often subvert initial premises, with Helck beginning as a comedic tournament narrative before evolving into a darker epic about betrayal and loss. Nanao's artistic identity is also marked by connections between series, as both Piwi and Völundio share the fictional universe established in Helck.

In 2015, Nanao received recognition at the Next Manga Award, where ACARIA ranked eighth in the web manga category and Helck ranked eighth in the print manga category, making Nanao the only creator to place in both categories that year. Helck also placed fifth in the 2017 edition of the web manga award This is the Really Interesting WEB Comic That One Million People Choose. The series has been licensed for English publication in North America by Viz Media, which began releasing a new edition with color pages and updated covers in 2023.