The Other Demon.

Kiss

"They are your flames. The reason you were consumed by your power when your sword cracked is because you became afraid. Afraid of what your friends would think, afraid of them being hurt, of your brother being hurt. Your fear took over disguised as rage."

"So, what? I need to forget about my friends and brother?" Rin asked, angry.
"In a sense. You need to let go of the fear of them getting hurt. Here, I asked Mephisto for some help." Isoya set some Frisbee looking discs down on the floor of the room they were in. Holograms of Rin's friends and family were on the floor, bloody and beat up. "This is what you fear, isn't it?" Isoya said quietly.

Rin looked around, the gashes and blood everywhere. "This looks like... they were cut down with something curved." Rin said.
"Oh, you noticed." Isoya chuckled.
"You didn't..." Rin trailed off.

"Oh, of course not. Not really." Isoya sliced his sythe through the illusion of Yukio. The head came off and rolled.
"Shit, Mephisto, you really went all out on this, huh?" Isoya said.
"Very realistic." Rin said, his flames trying to leap out. "Here. Let's reset these." Isoya slashed through all of the illusions. They all reappeared standing back up and looking normal. They even chatted together. Their words hushed whispers.

"Alright, let's say I'm some demon coming after you, okay? I'm going to try to use your friends and brother against you." Isoya said.
"You are going to use your flames to attack me as I do. I'll heal fast, so don't worry. It'll only make it harder to control." Isoya said. He stood still for a second before he rushed toward Yukio. He slashed at Yukio's stomach, but Rin blocked it. "Damaging your body isn't good, either you know. If you do that, you'll die before you hit 25." Isoya said.

He ran at Shiemi and slashed at her too, but again, Rin was there, he grabbed hold of the side of the blade with his hands, almost as if he were clapping. "Smart move, but leaves you at a disadvantage." Isoya said, pulling Rin and swinging the blade over his head. Rin landed on his back with an 'oof'.

"This isn't just combat, you know that, right?" Isoya said, pinning Rin to the floor with his sythe. "Use your flames. They can do more than you think." Isoya said, fully shifting into his demon form. His eyes were a dark, stormy grey, his teeth elongated, and electric, skeletal looking wings formed on his back. "You'll have to if you want to save your brother." Isoya quickly turned and slashed at the hologram, it cut in two and fell to the ground. The residual electricity from the sythe made it twitch.

"Yukio!" Rin shouted, his flames growing brighter and more deadly. He got up and hit Isoya. It left a burn on his face that quickly healed. "That's it. Let's see if you can actually aim your flames to attack." Isoya grinned. Rin growled, pissed as all hell. He threw his hand forward, throwing a wave of flames at Isoya, who moved over to the right, revealing Shiemi behind him. Rin's eyes went wide and he threw his hand to follow Isoya.

His flames followed. Isoya turned off the holographic machines. "Good." Most of his shirt had burned away from the flames. He took off what was left of if and smiled. "That was good." Isoya said. Rin punched him again, this time without the flames. Isoya flew backwards, but landed on his feet. "I know I deserved that."
"If you think, for one second, that I'll accept you after this shit, you're wrong. Dead wrong." Rin said, anger still flaming in his eyes. Isoya froze. "I didn't want this either you know. Your biological father would kill me if he found out. And that would start a war in Hell itself." Isoya said.

"Then why didn't you reject me? You said that either one of us could reject the other!" Rin yelled.
"I don't want to go to Hell!" Isoya yelled back. "Did you miss that part? The rejected mate will fade back to Hell for eternity after their mate is happy." Isoya said, turning away from Rin.

"You aren't the only one who hates their father you know. My old man is the only father I have ever known. And he's awful. When he took over my own mother and lied to me to coax me into accepting that I was a demon and to try to make me like him, I. Hated. Him. I rejected him and what he told me, and in turn, he made me watch my mother die. He forced her to take a blade and drag it across her own throat, her last words to me being, 'Run. Now!'" Isoya said, pinning Rin against the wall.

He stared at Rin's eyes. His own a steel grey. Rin had calmed down. "Hey, um, I'm sorry. For what I said a few seconds ago." He said quietly. Isoya sighed.
"You don't have to apologize. I do. I went too far today." He said, just as soft. He leaned his head on Rin's shoulder, closing his eyes and took a couple deep breaths. He lifted his head again and saw Rin was flushed. "You okay? Are you sick?" Isoya asked, feeling Rin's forehead. "You're not overly warm or anything." Rin flushed deeper. Isoya smirked, realization dawning. "Is it the fact I don't have a shirt on?" He whispered. Rin turned bright red at Isoya's keen observation. Isoya chuckled and pressed his lips against Rin's briefly. "See you tomorrow for more training." He said, walking away, tail swinging around.