Usokui is a manga one-shot created by Sako Toshio, in 2005, for Weekly Young Jump's 48th Manga Grand Prix competition. It won an honorable mention and was later published in the 48th issue of the magazine, that same year. The one-shot serves as a prototype for what eventually became Usogui.

Note: Republished in split-up sections as side stories for volumes 12-15 of Usogui as Igyou Tobakusha Usokui.