In this AU, things are switched. Yukio grows up normally and Rin grew up training. He became an Exorcist around thirteen. He's not a teacher. Rin has his own rank, so he's just the Weapon of the Order.

He's got Knight, Tamer, and Dragoon under his belt. He'd never go for Aria since he falls asleep having to read the Bible. Doctor would be his best bet if he were to go for a fourth Meister.

Yukio, Rin, and Shiemi work together to study to earn Doctor Meisters. Rin helps Shiemi with her tamer Meister and Yukio with his Dragoon Meister. Shiro is super grateful for that because as the Paladin, he's too busy to train Yukio.

The Senior Exorcists treat Rin like garbage and have repeatedly spit in his face and pulled his tail if it was out around them. Rin doesn't tell anyone because he's a big boy and he doesn't need anyone babying him.

After one too many insults that cut deep, Rin broke a guys arm and both of his legs, then have him a concussion via slamming his head into the wall.

"I earned my place. I've spent my entire life training to be as strong as they need me to be. Next time you insult me, I'll break your ribs until you're able to suck your own dick with how many ribs you'll lose." Rin growled out. It wasn't like him and was borderline monsterous, but he was done with this. He'd been raised in a country where anyone could be anything. He wouldn't take torment from a country that shunned him for being born. His mother's country.
If all Rin could be was the Weapon of the Order, then he'd wear the title with pride and demand respect from the weak humans that made up this organization.