The Masks We Hide Behind (Amaimon x Rin)

Chapter 1

When Rin was nine years old, he was diagnosed with anemia. He had been having nosebleeds often, and Shiro had decided to take him to the doctor. The doctor, having heard Rin got into fights often, asked about the injuries he received from said fights. Shiro told the doctor that he bruised easily, and that when Rin got cuts from the fights (or anything else mind you) they often bled a lot, no matter the size. Topped with the nosebleeds he quickly concluded that the boy had a minor case of anemia and prescribed iron supplements. Shiro had thanked the doctor and left, hoping his son would get better.
Rin never did. He actually got worse throughout the years, but he never told anyone, not wanting to be a bother. For the next few years, he took the supplements as he was told to. He never told Shiro they did nothing, and made sure no one else, especially Yukio would find out.
The symptoms were getting worse. The nosebleeds happened often, and his gums would almost always bleed. He was constantly fatigued and often irritated, but he never told anyone about the new symptoms.
Then, it happened. Shiro was killed by Satan because of Rin. He joined the Cram School to train to beat Satan. He actually made friends with the other students and had started rebuilding the broken bond he had with his brother, he was so happy. But, his condition became harder to hide. Then, the events with Amaimon happened, and everyone found out he was the son of Satan. He began training his powers with Shura and the Gehenna Gate incident happened. No one seemed to notice that he had bled far more than he should have. After he and Yukio defeated Satan, everyone went back to normal. Not wanting to focus on what happened.
In their haste to do this, no one noticed how much worse Rin was doing. The bloody noses and bleeding gums, topped with an almost constant fatigue were so much worse. He was able to hide the bleeding and bruising, and whenever someone saw how tired he was, they would brush it off as typical Rin. But, he was actually doing so poorly that he decided it was best he see a doctor.
The doctor, when having heard his patient had anemia with symptoms that had worsened since when he was first diagnosed, immediately ordered a bone marrow biopsy. What he found was shocking.
The results showed that Rin Okumura did not just have anemia, he had the most severe case of chronic idiopathic aplastic anemia that the doctor had ever seen. Rin didn't see how this was much different than what he was diagnosed with. They were both anemia? What was the difference?
"I'm not sure I understand doctor. How is this different from what I was first diagnosed with?" Rin asked.
"You were first diagnosed with regular anemia, an iron deficiency. Idiopathic aplastic anemia is when you're bone marrow stops making new blood cells. It's cause is unknown. I'm so sorry to say this, son, but you have a chronic condition of it. If it was acute, it would be much easier to treat, but with how long it's been left untreated there's not much we can do." The doctor told Rin. "We can still offer you the treatments though. Untreated chronic aplastic anemia is almost impossible to cure, but we could try.
Rin spoke after some time. "No thanks doctor. I think I'll forgo all treatment."
"Why?!" The doctor frantically asked.
"I already know I'm not going to make it. I'd rather not give my friends false hope to only crush it in the end. Thank you very much doctor. Goodbye." And with that, Rin left.
The next day, Rin acted completely normal. Not at all like he had just got the news that he was dying. He didn't want to leave the people he had come to care about with sad memories of him.
Yukio got a long mission after class, so Rin was left in the dorm all alone. He quickly gave up on homework, the fatigue impossible to work through. It was at this point that he finally broke down. Rin sobbed himself to sleep that night.
When he woke up that morning, he was quite thankful it was the weekend. He had slept quite late and was feeling worse than ever from how he had fallen asleep. Then, the coughing began.
Being a demon, Rin had never had a cold before. But, he remembered his condition caused him to be more susceptible to infections. Shit! He probably had a cold now.
Then he felt something coat his hand. He looked at it and saw blood. Most likely a mixture from coughing and his now bleeding gums. The familiar dripping from his nose had begun as well.
As he continued coughing, he heard something he didn't expect to hear. Someone was opening the window.
"Rin, I want to play!" Amaimon somewhat whined.
It was then he saw the other demon in the fetal position coughing up blood. It was all over his hands and clothes, dripping from both his nose and mouth.
When Rin realized that it was Amaimon. He feebly tried to grab his sword. But what Amaimon said next made him freeze.
"Why didn't you tell anyone you were this sick?"
"What makes you think I'm sick? I could have just been beaten up before you came? Besides, why would you care if I was sick?" Rin used most of his fading strength to reply, and collapsed back onto the floor. Amaimon quickly ran over to him.
"You honestly thought someone wouldn't notice how different you've been acting? It was easy to figure out something was wrong. Besides, why wouldn't I care?" Amaimon spoke all of this softly in Rin's ear.