Koi is a Japanese manga artist and illustrator known primarily for creating the popular four-panel manga series Is the order a rabbit? The creator, who is male and resides in Tokyo, began his professional career in earnest when his most famous work gained unexpected popularity. While Koi was active on the online art platform Pixiv before his major debut, details about his life before 2011 are limited. In a 2021 exhibition, it was revealed that Koi may be a collective pseudonym for two individuals working together, but their identities remain officially undisclosed.

Koi is the sole author of the long-running manga series Is the order a rabbit? (Japanese title Gochuumon wa Usagi Desu ka?), which began serialization in Houbunsha's Manga Time Kirara Max magazine in March 2011. The series follows a group of girls who work in coffee shops in a European-style town and has been collected into multiple tankoubon volumes. The work has become a significant title in the slice-of-life and comedy genres.

The manga has been adapted into several successful anime productions. The first anime television season, titled Is the order a rabbit?, aired from April to June 2014 and was produced by studio White Fox. A second season, Is the order a rabbit??, followed from October to December 2015, co-produced by White Fox and Kinema Citrus. The third season, Is the order a rabbit? BLOOM, premiered in October 2020 and was produced by Encourage Films. Beyond the television series, the franchise includes two animated films. Is the order a rabbit?? Dear My Sister was released in theaters in November 2017, and Is the order a rabbit?? Sing For You was released as an original video animation in September 2019; both were produced by studio production doA. Koi himself contributed to the screenplay for Dear My Sister.

Koi is known for a distinctively cute and detailed artistic style. The creator demonstrates a strong proficiency in drawing backgrounds and small props, and primarily uses the software Paint Tool SAI for illustration work. A recurring theme in Koi's personal work is an affection for magical girls, and floral imagery, particularly flower petals, often appears as a decorative motif. Before his own work was adapted, Koi contributed end card illustrations to several other anime series, including Hidamari Sketch, Yuyushiki, and Koufuku Graffiti. Koi has also provided illustrations for light novels, including the two-volume series Mahou Shoujo Kinshi Hou, and has worked on character designs for video games.

Koi holds a significant place in the manga and anime industry as the creator of one of the defining works of the "kirara" style of cute-girls-doing-cute-things. Is the order a rabbit? is a flagship title for Houbunsha's Manga Time Kirara brand and has maintained a consistent and dedicated fanbase for over a decade. The franchise's continued production of new anime seasons and films long after the manga's debut demonstrates its lasting commercial and cultural impact within the slice-of-life genre.