Catalyzes the NADPH-specific reduction of 1,5-anhydro-D-fructose to 1,5-anhydro-D-mannitol. 1,5-anhydro-D-mannitol + NADP(+) = 1,5-anhydro-D-fructose + H(+) + NADPH Monomer. Belongs to the Gfo/Idh/MocA family.