When he started at the company in 1989, he began with an anthology of various shorts and one-shots collectively known as Shiina Department Store.
Eventually one of these one-shots, about a beautiful, money grubbing female exorcist and her lecherous companion, would become the basis of his best known work: Ghost Sweeper Mikami: Gokuraku Daisakusen!!
[1] Even as he had success with Mikami, Shiina continued to create various one-shot stories on the side of his main series.
After the end of GS Mikami, Shiina tried to create new series for the manga anthology, such as Ichiban-yu no Kanata and Mister Japan.
(an alternate take on Sherlock Holmes co-starring the robotic Maria from GS Mikami) In 2003, Shiina introduced another of his many ideas in Shōnen Sunday in short form: Zettai Karen Children, about three young girls with great psychic powers and terrifying ambitions.