Mugichatarou Nenjuu, also known by the Japanese name 年中麦茶太郎, is an original creator working primarily in the light novel and manga industries. The creator is credited as the original author behind several fantasy series that have been adapted into manga versions.

Nenjuu is the original creator of the manga Kenshi o Mezashite Nyūgaku Shita Noni Mahō Tekisei 9999 Nandesu Kedo!?, which began publication in 2016. The story follows Laura, a young girl who trains to become a swordsman only to discover her magical aptitude is an unprecedented 9999. For this series, Nenjuu is credited for the story, while the artist Riichu provides the artwork.

Another notable original work by Nenjuu is Maou no Musume wa Sekai Saikyou Dakedo Hikineet! ~Hai Kyōkai ni Hikikomottetara Megami-sama to Shite Shinkou Saremashita~, also known as The Demon King’s Daughter is the World’s Strongest but a Shut-In! This series began as a web novel in 2017 and follows Iris, a biological weapon created from the Great Demon King's genes who abandons her mission of destroying humanity to live as a shut-in in an abandoned church. The light novel editions were published by Softbank Creative.

In 2016, Nenjuu also worked on Yuusha to Kenja no Sakagura, providing the story while artist Neko Nekobyou handled the illustrations. Additional works include Saikyō Ken Sei no Mahō Shugyō, which received both a light novel and a manga adaptation, as well as Seisan Shoku Level MAX kara Hajimaru Honobono Isekai Life, a manga published under the comic Spira label by Funguild starting in 2024.

Across these works, Nenjuu consistently writes in the fantasy genre, often featuring protagonists with overwhelming or unconventional abilities. The creator's works typically originate as web novels or light novels before receiving manga adaptations, a common trajectory in contemporary Japanese publishing. The creator maintains a consistent presence in the isekai and fantasy comedy subgenres.