Q.E.D. ~Shoumei Shuuryou~ is a detective fiction manga by Motohiro Katou. The main character Sou Touma encounters a variety of crimes ranging from murder to fraud. Sou often works in tandem with his friend and potential love interest Kana, with him supplying the brain while she acts as brawn. The title comes from the Latin phrase quod erat demonstrandum. Sou will typically write the term down when he has solved the case just prior to his explanation. In addition, the manga incorporates many terms and ideas from history, mythology, biology, mathematics and physics.