In the present regional monograph 848 specimens of Cerithiopsidae and Newtoniellidae of the Shouji Tsuzuki collection are analyzed. This work lead to the identification of 92 different species of which 21 are new to science. For 59 species the distribution range is expanded to Okinawa. 139 specimens are not determined to species level because they were only represented once and often were in bad condition. Fifteen genera of Cerithiopsidae are represented: Belonimorphis (with 1 species), Clathropsis (19), Granulopsis (1), Horologica (15), Joculator (17), Mendax (1), Marshallopsis (1), Ondulopsis (2), Oparopsis (2), Prolixodens (2), Retilaskeya (1), Seila (4), Specula (12), Synthopsis (13), Tubercliopsis (1), and two genera of Newtoniellidae: Ataxocerithium (1), Cerithiella (1). New taxa: Clathropsis albida n. sp., Clathropsis araii n. sp., Clathropsis fulvocincta n. sp., Clathropsis iheyaensis n. sp., Clathropsis matsukii n. sp., Clathropsis okutanii n. sp., Clathropsis zamamiensis n. sp., Horologica teruyai n. sp., Joculator aterrufus n. sp., Joculator fulvaster n. sp., Joculator hasegawai n. sp., Joculator kuboi n. sp., Joculator mitsuoi n. sp., Oparopsis hikimarum n. sp., Oparopsis tsuzukii n. sp., Specula churamaris n. sp., Specula naoae n. sp., Specula seragakiensis n. sp., Synthopsis shoujii n. sp., Cerithiella kaitotsuzukii n. sp.