Katya did that under Medis' wishes. While she's skeptical at first, Seeing Akira's true talent and powers (which exceeded Medis' stories) only further reinforced the idea that Akira should be in the kingdom putting his powers to good use.Seems they are more worried about him being manipulated by the foreign countries he spent a lot of time living and studying in. Also take into account that he has ambition enough to seek to claim the throne that originally only went to princesses, the attempt at Medis's life and he was able to convince the current queen to give him a legit bid for the throne and yeah even if he's not evil he is very much a threat in a sense.
Now granted, this does not make him a bad guy. He could have used those other countries as a means to strengthen and educate himself for the sake of his country, he legitimate believe that the country needs a ruler who is powerful in magic to combat the current threat (which as far as we know, Medis is not), he could have had nothing to do with what some fanatic members of his faction attempted on Medis and not to mention, Katya (though they tried to downplay it) is not entirely trustworthy, is a hypocrite, narrow-minded (same as she claimed Akira to be), and willing to do underhanded stuff to get what she desires (tbh though, I would have gladly fallen into that honey trap, she IS pretty hot). Oh and she's a liar, she was doing exactly what Medis thought she was doing and in fact trying to do something indecent.
One thing to know is that if your child has a magical potential he should study in the magic academy. The only reason akira didn't is because his mana broke and he pretty much hide it but now that it's been known, he should abide to the law of the kingdom as dirty selfish it might be. It also one of the reasons why Medis thought Akira was mad at her. Don't get me wrong tho, What they did is not good, but Medis really just pushed into corner to the point she has to broke the promise she made with akira.
As to why Medis broke the promise, you'll see in the later chaps why she was forced to play Akira to the table.