We have designed a new class of single-stage Faraday isolators that employs two sheets of graphene. Using nonreciprocal optical materials such as InSb boosts plasmonic coupling between the graphene layers, which leads to a 45 deg polarization rotation as well as increased transmission through the structure. More than 91% transmission is achieved in the THz band (1 THz-7 THz). This design opens up the way in ultrafast integrated magneto-optical nanophotonic devices to realize single-stage isolators with enhanced transmittance in the THz band.