His debut work, 137th Mobile Brigade (137機動旅団, Hyakusanjūnana Kidō Ryodan), was published in the March 1979 issue of Kisō Tengai magazine, for which he won an honorable mention in the 2nd Kisō Tengai SF Rookie of the Year Awards in 1980.
He published Planet CB-8 Wintering Party (惑星CB-8越冬隊, Wakusei CB-8 Ettōtai), beginning his close association with hard science fiction adventure novels.
In 1987, Tani's Martian Railroad 19 (火星鉄道一九, Māshan Reirurōdo Ikkyū) won the Seiun Award for "Best Japanese Short Story of the Year".
[5] He won the Seiun Award for "Best Japanese Novel of the Year" in 1994 for Endless Search for the Enemy (終わりなき索敵, Owarinaki Sakuteki).
[6] He won "Best Japanese Novel of the Year" again in 2007 for Japan Sinks: Part II (日本沈没・第二部, Nihon Chinbotsu Dai-ni-bu), which he coauthored with Sakyo Komatsu.