During a shogi game called "Ryujin-sen," 8-dan Tonezawa (Yasosuke Bando) attempts to cheat. When one of the overseers, Oishi (Shoji Kobayashi) confronts him about the ploy, Yonezawa kills him and fakes it as an accident. The game later continues as a memorial to Oishi, but Furuhata, who came to inspect the scene, begins to suspect murderous intent in the unnatural scene.
将棋の「竜人戦」で、米沢八段（坂東八十助）はどうしても負けたくない一心で不正を行い、それを指摘した立会人の大石（小林昭二）を殺害して、事故死したように偽装する。大石への追悼として対局は続行されるが、現場検証に来た古畑は現場の不自然な状況から事件性を疑いだす。
