NXT Capital LLC has agreed to manage Aflac Inc.'s new portfolio focused on investments related to middle-market private debt.

Aflac unit Aflac Global Investments will initially fund a $500 million portfolio consisting of direct investments in floating rate, senior secured loans to middle-market companies on behalf of the insurer's general account.

Additionally, Aflac will invest roughly $50 million for a minority stake in NXT Capital. The investment will be funded from Aflac's insurance general account.

"Aflac made a strategic asset allocation decision to utilize floating rate assets as a core part of its hedged U.S. dollar program for Aflac Japan," Eric Kirsch, Aflac's executive vice president and global chief investment officer, said in a news release.