Japanese ultra-long-term government bonds rebounded on Wednesday, halting a steep decline triggered earlier this week by concerns that upper house elections could drive higher government spending. The yield on 30-year bonds fell 10 basis points to 3.06%, while the 40-year yield similarly retreated 10 basis points to 3.38%. This recovery followed Tuesday's surge that pushed 30-year yields to their highest level since 1999.

"This buying wave clearly responds to yesterday's sharp sell-off," noted Katsutoshi Inadome, senior strategist at SMBC Trust Asset Management. "While markets remain watchful over potential post-election fiscal stimulus, the yield surge has temporarily paused as investors await election outcomes."

Mounting pressure on Japanese government bond yields continues as the July 20 election approaches. Prospects that the ruling coalition might lose its majority have intensified fiscal uncertainty. Strategist Mark Cranfield observed: "With USD/JPY touching three-month highs and traders positioning for a potentially chaotic upper house election this Sunday, JGB yields face sustained upward pressure."

The Bank of Japan's gradual reduction of its massive bond-buying program, coupled with domestic mega-insurers not filling the void, has further propelled yields upward. "Pre-election political anxiety persists, but markets appear to have completed a phase of selling," commented Michael Brown, senior research strategist at Pepperstone. "Markets will likely take a breather to assess election results before taking further action."