What is "tonkori"

The is a plucked string instrument played by the Ainu people of Hokkaidō, northern Japan and Sakhalin. It generally has five strings, which are not stopped or fretted but simply played " open". The instrument is believed to have been developed in Sakhalin. By the 1970s the instrument was practically extinct, but is experiencing a revival along with the increased interest in Ainu heritage.