Nakaumi (中海) is a brackish lake located between Tottori and Shimane prefectures in Japan. The lake is enclosed by the Shimane Peninsula to the north and Yumigahama Peninsula to the east. It is the fifth largest lake in surface area in Japan.Nakaumi connects Lake Shinji (宍道湖 Shinji-ko) and the Sea of Japan, and is surrounded by the municipalities Matsue, Yasugi, Yonago and Sakaiminato.There are two large islands in the lake, Daikon Island (大根島 Daikonjima, lit.