In the novel, the imperial knights weren’t loyal to the crown. Most of them were dispatched by noble families who were staunch adherents of the Ducal houses. 

The Hexagon Order has 6 battalions under it: 

The White Pearl Order of House Honesto,

The Citrine Order of House Adinerado, 

The Emerald Order of House Sabiduria, 

The Lapiz Lazuli Order of House Juicio, 

The Red Diamond Order of House Coraje,

and 

The Purple Topaz Order of House Benevolencia (Hmm let's save that for later)

There are many prominent figures who will betray the crown. Gaston Adinerado, the uncle of the male lead and the Head Commander of the Purple Topaz Order. Yes, he’s an Adinerado and should be serving the Citrine Order (Adinerado knights), but since he’s the 3rd son and didn’t have a claim on the duchy, his brother Duke Lucio Adinerado asked him to become a knight of the imperial family to spy on them. Sadly, the Ducal houses can place whoever they want in whatever position they find useful. Gaston is a swordmaster, but with no war for a thousand years, despite his mastery, he lacks experience in real combat.

In the novel, Gaston is portrayed as an insecure “man-child” who looks down on the imperial family. He was the one who trained the crown prince, always ensuring he got wounded. It’s the reason why Prince Gavino has low self-esteem. He constantly utters degrading words like “Are you sure you’re of the imperial family line?” or “You’re just mere figureheads; if Duke Adinerado hadn’t asked me to become one of your knights, I wouldn’t have said yes.” There was even a time when the crown prince returned home with his right arm broken and was mocked by the imperial army itself. sigh What a load of rubbish.

I'm heading now to the captain’s underground office. It's where one of the training arenas is situated.

The place doesn’t resemble a training arena at all; it’s extravagant, adorned with gold and various jewels. The knights pass by without greeting me, knowing I'm from the imperial family. Just so you know, it’s a knight's etiquette to greet the family they serve. I guess Gaston did a good job eroding the knights' loyalty to the crown.

I'm finally outside the captain’s office.

Knock, knock

Someone opens the door.

“May I inquire what you need, Your Highness?” one of the knights asked.

“I would like to see Captain Gaston. Thank you.”

“Just wait a while, Your Highness.”

“The level of disrespect. It’s been almost an hour now, Esteban (Royal family’s butler).”

Suddenly, a noble lady exits his office, glaring at me as if I’m insignificant. She doesn’t greet me.

“Duratus (Freeze in Latin).” I paralyzed her.

“Your Highness…” Esteban looks worried.

“Hey, you! You’re not even from one of the 6 main houses, yet your level of disrespect knows no bounds.”

“Genua (Kneel)!”

“Your Highness, I think you’re…”

“Esteban, should I tolerate any level of disrespect to the imperial family?”

“No, Your Highness.”

“Bow your head to the ground.” It’s a magic spell that will immobilize her. I step on her head, emanating a powerful aura called “Timeo (Fear).” I ensure she won’t be able to speak, although she’s crying. But what can I do? I was once a commander in my past life; I have a superiority complex.

“Listen, noble lady whom I don’t know and have no interest in knowing. Never, ever disrespect a member of the imperial family. You’re lucky I didn’t sever your head.” These people here are infuriating me.

“Your Highness, please calm yourself.” Esteban holds my arm as I head toward Gaston’s office.

“I'm sorry, Esteban, I’ve reached my limit.” Sorry, Esteban, but people in the army know me as the Rabid Healer. I'm a ferocious dog in battle but a healer to my colleagues who need treatment.

"Oops! I broke your door."

Let the purging begin.