To me it feels like that bit on the start was a reverse card foreshadowing. I don't think the princess is directly responsible but being manipulated by Boku. In the start we learn the almost-exclusive use of male ajin as beast-servants is caused by a past issue where a female ajin was a servant and used her master to hold power. The narrative also makes sure to criticize the gender inequality regarding ajins. So I wouldn't be surprised if Boku (a male ajin) was doing the same as the female ajin because being manipulative isn't related to gender at all. And probably something about ajins only doing that sort of thing because they have no direct access to power and probably a big ajin conspiracy considering they are the strong military force in that world (also probably foreshadowed before).