"Y-you! Have made your point! At Least call a healer for me so I can get away from you!" 

Kurosu was nearly in tears. He was sure all his bones in his foot were nothing but mesh at this point.

Shiro hovered over him. A brilliant plan formulated in his mind.

"How about we make a deal, Jerkface" 

Kurosu was about ready to throw up from the pain.

"What the hell is wrong with you!"

"This will work for you so just hear me out!" 

"What is it then! I can't even move!"

Shiro smirked as he moved closer to Kurosu and his injury.

"If I heal you, will you take me on as your apprentice?"

Kurosu looked like he was ready to die from second hand embarrassment.

"...Did you escape from a mental asylum?"

"Hey! I'm being serious! I can heal you!"

"You can't heal me, you idiot! Your mana doesn't mix with mine! Go get a real healer! Your just wasting my time"

"That's bullshit! I've healed loads of your kind before!"

Kurosu was on the verge of death, he must be hallucinating this. He was sure of it.

All dragons know that every dragon's mana is unique and holds different properties. Green Dragons mana can mix together with another's to speed up the process of healing. Blue Dragons can use their ice to freeze another. But there's one problem for when Black Dragons are used. Their mana is too poisonous to be mixed and can even cause blight on the recipient. White Dragons can purity it but due to their conflicting elements, they clash and will nullify can mixing. 

"How can this White dragon lunatic think he could heal him!?! He must be out of his mind!!" Kurosu thought to himself.

"I'm serious about this!" 

"Just stop! Call for a real healer!"

Shiro grabbed his injured foot.

"Aha-!!"

Kurosu yelped in intense pain

"Listen to me! If I can heal you, which I can, will take me on as your apprentice! I'll do whatever you ask of me! I need this!!"

"...and if it doesn't work?"

"...I'll call for a real healer and I'll nullify the contract"

".....you swear?"

"Dragons don't lie! I swear on my life's blood!" 

Kurosu held out his left hand. Shiro took it. Signifying the swear upon his blood.

Shiro couldn't help but notice Kurosu's long black nails and cold hands that felt like death.

"....fine"

 Shiro got to work as he gently pressed his hands on Kurosu's limp and mangled foot. A light teal aura engulfed Shiro's hands as his mana flowed into them.

Kurosu felt warmth around his body. The sensation felt good, not what he had expected. 

His foot began to reform, bones piecing themselves back into place and tendons uncoiling from the strain. It didn't hurt, not like it would if it had healed on its own, which normally takes two or even three days for a healthy dragon. It felt incredibly relaxing. This aura. He's never felt it before.

It wasn't like a white dragon's aura, which was suffocating Kurosu. This one felt warm and soothing. Like a springfield. 

"Done." Shiro proclaimed, pulling his hands away from Kurosu.

The taller dragon felt no more pain in his foot. He sat up and saw that his foot looked perfectly normal. Only minor dusting on his shoe from where Shiro had pressed on the top. It was like nothing had ever happened. 

"See!?! I told you I could do it! I swore, didn't I!?!" Shiro exclaimed proudly. "Now I'm your apprentice! HaHaHa!!!"

"How did you do that!?!" 

Kurosu stood up slowly, trying to check if what Shiro had done had actually happened.

He walked slowly and felt no pain in his foot. Nothing out of place at all.

Shiro stood up as well and kept proudly spouting about his skills.

"I'm just that good! I can heal just about anything! And you didn't even believe me!"

"Your smell...it's definitely pure blood"

Kurosu, like all dragons, has keen senses. He could smell the scent of pure blood. The smell is stronger than that of a halfling or weak blooded dragons. 

Pure Bloods are few and far between so it's hard to fake a scent of one. 

"No wonder Koen wanted him so badly. Pure Blooded White Dragons are hard to come by" Kurosu thought to himself.

"I don't why it matters that much but yeah, I'm pretty sure I'm one. Both my parents are white dragons." Shiro answered.

Kurosu grabbed Shiro's wrist. 

"Come with me"