Mugen is a member of Danzō Shimura's Root faction in Konohagakure. After Danzō was revived and secretly returned to the village one of his goals were to eliminate any surviving Uchiha and harvest their Sharingan. Now during the Chunin Exams being held in Konoha, Danzō dispatched Mugen to retrieve the Sharingan of the Uchiha Clan members participating in the Chunin Exams, including Team Uchiha and Sarada Uchiha.