TOKYO, Aug 26 (Reuters) - Yields on benchmark 10-year Japanese government bonds reversed early gains to stay unchanged on Thursday as the market witnessed a solid outcome of a 20-year note auction. The 10-year JGB yield was flat at 0.015%, after rising to 0.025%. The auction for 20-year notes drew bids worth 3.65 times the amount sold, higher than a bid-cover ratio of 3.51 times at the previous auction. Yields on longer term notes fell, with the 20-year JGB yield losing 0.5 basis point to 0.400%, and the 30-year JGB yield falling one basis point to 0.635%. The 40-year JGB yield also fell one basis point to 0.715%. The two-year JGB yield rose 0.5 basis point to minus 0.135% and the five-year yield was unchanged at minus 0.120%. Benchmark 10-year JGB futures fell 0.02 point to 152.21, with a trading volume of 21,093 lots. (Reporting by Tokyo markets team; Editing by Krishna Chandra Eluri) Our Standards: The Thomson Reuters Trust Principles.