SoftBank Group Corp. is considering a sale of Fortress Investment Group, according to people with knowledge of the matter, as the Japanese conglomerate reviews options for the asset manager it acquired four years ago.

SoftBank’s deliberations regarding Fortress are at an early stage, said one of the people, who requested anonymity because the matter is private.

The move is driven in part by the fact that the Japanese conglomerate was unable to mesh Fortress’s operations with its own, the people said. Representatives for SoftBank and Fortress declined to comment.