Japanese life insurance companies hold a large amount of Japanese government bonds (JGBs) as long-term investments. Recently, their holdings of super-long-term JGBs have been increasing especially significantly, and the presence of life insurance companies in the super-long-term JGB market has grown. At life insurance companies, future insurance payment accounts for a large part of liabilities, and thus the period until they make insurance payment (the maturity of liabilities) is long. The period of investment for asset management (the maturity of assets) is long accordingly to anticipate insurance payment. The maturity of liabilities has lengthened moderately as a whole and has remained longer than that of assets. The need to resolve such duration mismatch by lengthening the maturity of assets is one factor behind life insurance companies' active investment in super-long-term JGBs. However, future demographic changes may shorten the maturity of liabilities, and therefore demand for super-long-term JGBs from life insurance companies is likely to change accordingly.