Gains of stocks give investors another reason to sell bonds.
Koizumi's overwhelming victory was a surprise. Further gains in stocks will fuel optimism about the economy, pushing up bond yields.
Falling stocks can prompt some buying of bonds.
There was index-related buying as we approach the end of the month, lifting the debt market.
Investors, especially pension funds, have lots of cash set aside to buy bonds, and most of that money is still waiting to be used for purchasing debt.
The JGB market got a lift from a pullback in equity prices here, with bargain hunters emerging.