I´m pretty sure it´s the oposite what people are thinking, the princess has been hinting to have a thing fot the king for a long time now, or at least been aiming for marriage, her mother comments about Suya father also seemed marriage related...
Also... there´s been a lot of hints that Suya is actually older than the king, wonder if this will be a turn off to the demon monk.
And... the king is completely oblivous to all of that...he´s trully innocent.