The benchmark 10-year yield edged up half a basis point to minus 0.120 percent, while June 10-year futures ended nearly flat, down just 0.01 point at 152.16.
Japan's Ministry of Finance offered 800 billion yen ($7.44 billion) of 30-year JGBs with a 0.30 percent coupon.
The lowest accepted price was 99.45, with a record low yield of 0.320 percent. The bid-to-cover ratio improved to 3.42 from 3.01 at last month's sale, while the tail between the average and lowest accepted prices shrank to 0.14 from the previous 0.40.
The 30-year JGB yield fell 2 basis points to 0.275 percent , while the 20-year JGB yield shed half a basis point to 0.220 percent.