Promises
3rd P.O.V.
Rin was watching the sunset up on the abandoned boy's dorm. It was a bad day with every
one yelling at him about something that he can't control. Bon was the worst though, he kept mentioning the blue night and how Rin has no reason to become an exorcist. He said how all he'll never be able to do anything with his life and all that he'll ever be is a demon. He came up to the roof after to think and realized something important.
Just because people think he is a demon doesn't mean he needs to act like one. He can do what Shiro told him, use his power for a gentler purpose. Rin realized that just because people expect one thing, doesn't mean that he has to do that. He didn't try to do anything to his peers or Yukio even though they expected him to. He also realizes that just because you have the same DNA doesn't mean you are family. Family doesn't hurt each other, but Satan hurt him in the worst way.
Satan isn't, and never will be, Rin's father. A father is someone who helps you when you're hurt, in any way. He jokes with you and might embarrass you, but you know he loves you. The most important thing he does though is shows that he loves you by wanting to make you happy. Satan did the opposite. He took the person who loved Rin the most away. Family will do anything to see each other happy, but if you take away the most important person to someone, then you turn into an enemy.
Satan can never be family because he took away thw only father-figure that Rin had ever had. Shiro was the best father that Rin and Yukio would ever have. It isn't just because of him taking care of them and giving them advice for girls, but for helping them when they needed it most. He gave Rin a reason to do well at the interview. He motivated them to do there best. Rin said he wanted to be treated like an adult, but he needs to prove it first. One way to be an adult is to do something with your life. It isn't based on your age or intellect, it is based on actions.
He then smiled, "I will prove that I am an adult to you. That is a promise that I will never break."