Japan's super-long bonds experienced a dramatic shift in December, as insurers hit the brakes on their holdings at a pace not seen before. The month marked a turning point in the insurance sector's bond buying appetite, with sell-offs reaching record levels. This massive shift in institutional behavior signals growing concerns about the sustainability of Japan's ultra-long debt positions. For market watchers, the move reflects broader questions about how major financial institutions are repositioning across global fixed-income markets amid shifting economic conditions.