Some people mentioned it would be nice to get another person in, like Naokis mom. But like there was said, it would put much more work for the dev. So i think there actually already is another person, who can be corrupted. Yes its Naoki. Considering the technology the story and MC has, i would not be surprised, if there was a possibility to turn Naoki to woman, and i dont mean like now, but complete genetical transformation, like a pill that would gradually turn him into a woman or maybe a clone and moving the mind to new body. 
The corruption then would be for him wanted to be turned to a woman (the sead of that could be, because he wants still to be with the girls) and then of course loving the MC.