The Nikkei stock index ended up 3.2 percent at a more than two-week high.
In the superlong zone, the 30-year JGB yield was flat at 0.405 percent, after a relatively volatile session in which it fluctuated between a record low of 0.385 percent before the auction and 0.420 percent.
Japan's Ministry of Finance auctioned 800 billion yen ($7.33 billion) of 30-year JGBs, at a record low average yield of 0.388 percent.
The bid-to-cover ratio, a gauge of demand, fell to 3.39 from the previous sale's 4.21. The tail between the average and lowest accepted prices, another demand gauge, widened steeply to 0.67 from 0.03 at last month's sale.
The yield on the benchmark 10-year JGB was flat at minus 0.090 percent, while 10-year JGB futures ended up 0.05 point at 151.68.