Snow surrounds the 17-year-old Kazahaya Kudou while he fights not to lose consciousness amid the freezing landscape. Luckily, a cold-blooded young man named Rikuo Himura saves him and brings him to his boss, Kakei, owner of Green Drugstore. Out of necessity, Kazahaya agrees to become Kakei's employee.

However, Kazahaya's job is not limited to organizing shelves and dealing with customers. Due to his ability to see strange things, Kazahaya is commissioned to complete dangerous assignments in exchange for money. Begrudgingly paired, Kazehaya and Rikuo—who also seems to possess unique powers—must take on these missions while confronting ghosts from the past that are hunting them down.

Gouhou Drug was published in English as Legal Drug by Tokyopop from October 12, 2004 to June 7, 2005. Dark Horse later gained publishing rights to the series and republished it on September 30, 2014. It has also been published in French by Delcourt from November 1, 2003 to June 17, 2004; and in Spanish by Norma Editorial from November 2003 to December 2004.