Toshiki Yui is a Japanese manga artist and illustrator born in 1956 in Kyoto Prefecture. He began his professional career in 1986, initially publishing works under the pen name Masaki Kato before unifying his output under his real name. His early publications included science fiction and horror stories, but he became best known for his work in the seinen demographic, creating manga series that blend romantic comedy with supernatural and often sexually explicit elements.

Yui is credited as the original creator of Kirara, a manga series that was serialized in Shueisha’s Weekly Young Jump from 1993 to 1997 and compiled into six volumes. The story follows a young woman who dies in a car accident and returns as a ghost to interfere in the past relationship of her fiancé. This work was later adapted into an original video animation (OVA) released in 2000, representing one of the primary instances of his manga being adapted for the screen.

Beyond Kirara, his body of work includes numerous other series such as Kagome Kagome, Junction, and Hot Tails, the latter of which has been noted for its influence in the futanari genre. His style is characterized by a focus on bishojo, or pretty and sexy girls, often within the framework of erotic comedies. He is recognized for his early and extensive use of computer-assisted drawing techniques, particularly with a Macintosh, which gave his art a distinctive look. His work has been translated into multiple languages, including English and French, and he has maintained a long-standing presence in the industry, with his publications spanning from the late 1980s into the 2010s.