Just re-read everything - I forgot that Falanus was able to tame beasts - except his definition of 'beasts' include humans. Nanana was not affected thanks to the Null Status Ailments potion, and Falanus was even afraid that his ability would be revealed if Nanana did a Simple Analysis.
I guess Nanana must have picked up how unnatural it felt how all the Japanese people she knew in the opposing country was all over Falanus, even to the point of becoming his harem and doing everything to serve him... (cough Ken'ichi and his harem of Four Heavenly Kings cough - I get it, Ken'ichi did win his harem by beating them all up, and his harem follows him out of free will, but you gotta admit Ken'ichi and Falanus are really foils to each other.)