Ex-Demon King's Right Hand

Ryou spent the next few days training with both Hanzoku and Kushu and planning his strategy to save Kirihime.
“Listen well, boy.” Hanzoku said in the beginning of their training.
“Just call me Ryou.” Ryou interrupted.
Hanzoku frowned, but he continued. “This world has several layers of dimension that’s only accessible for beings with magical power. The demon realm is inside one of those layers. If you want to get in, you have to get some help. Fortunately, I can open those layers, though not for long.”
“Alright.” Ryou nodded.
“The demon king has a castle in the center of the realm. If he brought Kirihime-sama back, he’d put her inside the castle. I’ll give you the map of the castle later, so be sure to memorize it.” Hanzoku explained.
“Having the former right hand of the demon king sure is convenient.” Kushu commented.
Hanzoku made sure to smack him before resuming. “As you can expect, the castle is swarming with demons. I can teach you several tricks to defeat demons, but the problem lies in the demon king. I’ve told you that you can’t defeat him, so the best you can do is stalling him so that you can run away.”
“Run away?!” Ryou stood from his chair. “But...!”
“Boy, do you want to die pointlessly or do you want to save Kirihime-sama?” Hanzoku glared at him and Ryou sat again.
“Sorry. So you’re saying that I shouldn’t pick a fight with him.” Ryou said.
Hanzoku nodded. “If you really have to fight him, your only best chance is to hit him with a surprise attack from his blind spot. Even that won’t kill him, so use that chance to run away.”
“I...I understand...” Ryou unwillingly agreed.
“Hey old man, what is the demon king trying to do by taking the princess back?” Kushu spoke up.
“Now that you mentioned it, if Kirihime really is his daughter, then why let her come to human world in the first place?” Ryou frowned.
Hanzoku heaved a deep sigh. “Maou’s goal is just the same as those lowly humans’ goal. To create an army of artificial Mazoku. In order to do that, he went as far to create someone who could realize his dream. That person is Kirihime-sama. I think his preparation is finished, so she was brought back because he no longer needed her in the human world.”
“Just for that sole purpose...” Ryou clenched his fist. “He dared to use his own daughter as his pawn for her whole life...unforgiveable...”
“Now...” Hanzoku stood. “Shall we begin, Satomi Ryou?”
Ryou nodded. “Yes.”
Thus, Ryou spent the next few days with some hellish training—again—with Hanzoku and Kushu. Since Hanzoku estimated that they still have a week before Maou made any move, Ryou made sure he used every single second to prepare himself.
“Hey, Hanzoku...” Ryou called out after dinner, when they all lay sprawled on the grass to enjoy the night sky. “Why did you rebel against Maou?”
“Aah...it’s such a long story.” Hanzoku closed his eyes. “I used to be such a devoted knight to him, until he did something I couldn’t forgive. I opposed him and left the demon realm. I got this scar when I fought all-out with him but still forced to escape. You see, knights can’t serve someone who does things they can’t accept, no matter how precious that person is.”
Ryou looked at Hanzoku in surprise. “So you used to be his knight as well? That Kojou Maou?”
“Yeah, I’ve been with him since his youth. I’ve sworn to always stay by his side, but then he changed and I...” Hanzoku smiled bitterly. “I couldn’t change with him. I broke my own promise to him.” Then Hanzoku looked at Ryou. “But I’m truly glad Kirihime-sama found someone like you as her knight.”
Ryou quickly averted his face, feeling embarrassed and happy at the same time. “T-Thank you. You seemed to really treasure Kirihime.” He noted.
“Well, the reason why I rebelled is deeply intertwined with Kirihime-sama. Though I’m not her protector or anything, so I can’t stop people like this brat who want to take revenge on her.” Hanzoku slapped Kushu’s back.
“Then, what is your connection with Kirihime?” Ryou asked curiously.
Hanzoku smiled. “I’ll save that until you’ve met Kirihime-sama. After all, you haven’t heard the truth from her, right?” Hanzoku guessed.
Ryou looked at him in surprise. “Yeah...I’ve been too focused on saving her that I forgot about that.”
“You’re such a hopeless person, Ryou. No wonder you’re a wonderful pawn for the princess.” Kushu reprimanded him.
“I’m not...” Ryou lowered his face. “...a pawn.”
Hanzoku straightened himself. “You should sleep, Ryou. You’re going to the demon realm tomorrow after all.”
“HUH???!!!” Ryou instantly lifted his face.
“What do you mean ‘huh’? I’ve told you, right?” Hanzoku looked at him.
“Don’t joke with me!! You never said a thing about that!! You said we had a week!” Ryou argued.
“Ah, my bad. I mean we only have few days until a week at best. Did I just say a week?” Hanzoku tilted his head.
“Aah, whatever!! I’m more than ready to save her anyway, so I’m going to sleep first!” Ryou headed back to the mansion, since it wasn’t so far from Hanzoku’s house.
But that night, Ryou couldn’t sleep. He kept turning and tossing around, but his mind wouldn’t settle down. He kept imagining Kirihime was locked inside a prison in the dungeon—what kind of castle that didn’t have a dungeon?—or being tortured by a demon, desperately waiting for Ryou to save her.
“Wait for me, Kirihime.” Ryou swore in his heart. “I’ll definitely come and take you home with me...” He finally succumbed to the fatigue and fell asleep.