A/N: This will be a Rin x Shima fanfic. It is based off of the anime; therefor there will not be a Kyoto arc. The story will take place about 10 days after the twins defeated the Gehenna Gate.

If something is written in Italics it's a flashback, and if it is written in Bold its ether a conversation someone is having to themselves or just their thoughts.

Character Names belong exclusively to Kazue Katō. However everything else is MINE! (Evil Fanboy Laughing in the backgouund)

"Rin wake up!" called out the small black Cat Sith.

He looked at his owner and smiled, as he sat there waiting for Rin to awaken thoughts of his former owner Shiro filled his mind.

"Kuro what's wrong you use to love my Catnip Wine? Are you not feeling well?" even though he tried to hide it in his voice worry and concern were clearly painted on the old paladins face.

Looking up at his owner he gave a faint smile and said, "Its not that Shiro you see mating season has started for demons." Shiro's eyes widened at this news and looked a bit taken back. Quickly Kuro sat up and said, "You must not tell anyone, and humans can't know that demons mate."

Shiro's facial expirations quickly changed from confusion to serious than he asked, "Why is that could you tell me more."

"You see when demons enter mating season we emit certain odors that attract other demons and in some cases humans. Are energy levels get weaker and we can't defend are selves that well. For higher-level demons like Kings and Satan there energy levels don't drop but instead they increase. If exorcists were to attack the demons the stronger ones would attack and wipe out the exorcists!" The Cat Sith calmly explained.

"I understand I'll say nothing. Would you feel better if you were with Sr. Pheles?"

"No if I sleep and relax if should pass with in a day or two." With that the small Cat Sith was asleep.

Annoyed that his owner still wasn't awake he walked over to him with the intent to jump on him until he woke up. Fine if your not going to get up than ill just… wait that smell it can't be? Kuro moved in closer until he was inches away from his sleeping owner, his eyes widened when he realized what the smell was. That smell I'm sure of it now he has started his first mating season! I need to go tell Mephisto! Kuro jumped away from Rin and headed towards the door just as Yukio entered the room, he looked up at Yukio and quickly ran out the slowly closing bedroom door.

XxXxXxXxXxX

The tall calm Exorcist looked down at his twin brother with anger displayed on his face and in the tone of his voice as he said, "Brother how can you still be asleep its almost noon."

"Hmm. Yukio? What time is it?" The demon boy looked up at his twin not opening his eyes and asked his twin with a drowsy voice. He slowly opened his eyes to taken in the world around him it was sunny and summer was just starting and the warm sun and air came in across the window and shone on his face and body.

He looked over at his brother and said, "Its 11:30 in the afternoon. Now get up and go take a shower you stink!" The demon muttered a few curses under his breath as he got up and grabbed a towel. "I have to go see Moriyama to restock my supplies after our last mission so I won't be here when you get back." The Exorcist exclaimed, as his twin was moving around gathering his things. As he left he looked back to his twin and said, "Hmm. Ok."

What's wrong with Brother he smelt worse than ever this morning. I wonder if it's something to do with his demonic blood? I'll go see Sr. Pheles and ask him what's happening.

XxXxXxXxXxX

"Mr. Pheles we have a BIG problem" yelled out the Cat Sith as he ran into the Demon Kings Office. The demon in question was lazily looking out the window that gave him a view of the majority of the school grounds. He slowly turned in his chair to face the Cat Sith whom by now was settled on his desk. His comedic expression quickly faded and was replaced with a serious one when he saw the look on the Cat Sith's face. He asked in a hushed tone, "What's the problem? And be quick I sense that someone is coming." The Cat Sith quickly said, "Its Rin he has entered his first heat cycle." The Demon King simply nodded and said, "Ok you stay with him and I will handle things here. Thank you for telling me. Now go quickly someone is about to entre." With that the Demon King turned in his chair and the Cat Sith jumped out the open window and started to sprint towards his owner.

* Knock * * Knock *

"Yes Entre." The Demon King said as he twirled in his chair to face the door. "Mr. Pheles I wondered if I could have a word with you about my brother." Once again the Demon King turned deadly serious as he spoke "Yes about your brother what's wrong?" Yukio sat down on a chair facing the Demon King and calmly said, "Well you see this morning when I went to wake him I noticed that his muscles seemed more defined, his fangs looked sharper, his ears were pointer and his tail appeared to be longer. Also there was this horrific smell coming off of him."

The Demon King took a pause and than asked, "You could smell him? And how did he act?" Yukio looked concerned when he answered, "yes I could smell him and he acted his normal self maybe he was a little more moody but other than that normal. Why?" The Demon King straightened up in his chair and calmly explained everything about mating to Yukio he paid detail to the fact that Rin would become moody, would act different, how the change in appearance was to catch a mate, and how the smell is also to attract a mate however because Yukio found the sent unappealing that the twins wouldn't be falling for each other any time soon. Yukio straightened and calmly said, "I understand. You will explain this to Rin then." Mephisto returned to looking out the window and said, "I wont need to his demon instincts will inform him. Well some what." As Yukio was leaving he said, "I see but I will still keep an eye on him."